共查询到20条相似文献,搜索用时 24 毫秒
1.
M.B. Reine J.W. Marciniec K.K. Wong T. Parodos J.D. Mullarkey P.A. Lamarre S.P. Tobin R.W. Minich K.A. Gustavsen M. Compton G.M. Williams 《Journal of Electronic Materials》2008,37(9):1376-1386
This article reports new characterization data for large-area (250 μm × 250 μm) back-illuminated planar n-on-p HgCdTe electron-initiated avalanche photodiodes (e-APDs). These e-APDs were fabricated in p-type HgCdTe films grown by liquid-phase epitaxy (LPE) on CdZnTe substrates. We previously reported that these arrays exhibit
gain that increases exponentially with reverse bias voltage, with gain-versus-bias curves that are quite uniform from element
to element, and with a maximum gain of 648 at −11.7 V at 160 K for a cutoff wavelength of 4.06 μm. Here we report new data on these planar e-APDs. Data from a third LPE film with a longer cutoff wavelength (4.29 μm at 160 K) supports the exponential dependence of gain on cutoff wavelength, for the same bias voltage, that we reported
for the first two films (with cutoffs of 3.54 μm and 4.06 μm at 160 K), in agreement with Beck’s empirical model for gain versus voltage and cutoff wavelength in HgCdTe e-APDs. Our
lowest gain-normalized current density at 80 K and zero field-of-view is 0.3 μA/cm2 at −10.0 V for a cutoff of 4.23 μm at 80 K. We report data for the temperature dependence of gain over 80 K to 200 K. We report, for the first time, the dependence
of measured gain on junction area for widely spaced circular diodes with radii of 20 μm to 175 μm. We interpret the variation of measured gain with junction area in terms of an edge-enhanced electric field, and fit the
data with a two-gain model having a lower interior gain and a higher edge gain. We report data for the excess noise factor
F(M) near unity for gains up to 150 at 196 K. We describe the abrupt breakdown phenomenon seen in most of our devices at high
reverse bias. 相似文献
2.
Jeff Beck Milton Woodall Richard Scritchfield Martha Ohlson Lewis Wood Pradip Mitra Jim Robinson 《Journal of Electronic Materials》2008,37(9):1334-1343
The next generation of infrared (IR) sensor systems will include active imaging capabilities. One example of such a system
is a gated active/passive system. The gated active/passive system promises target detection and identification at longer ranges
compared to conventional passive-only imaging systems. A detector that is capable of both active and passive modes of operation
opens up the possibility of a self-aligned system that uses a single focal plane. The mid-wave infrared (MWIR) HgCdTe electron
injection avalanche photodiode (e-APD) provides state-of-the-art 3 μm to 5 μm performance for the passive mode and high, low-noise, gain in the active mode, and high quantum efficiency at 1.5 μm. Gains of greater than 1000 have been measured in MWIR e-APDs with a gain-independent excess noise factor of 1.3. This paper
reports the application of the mid-wave HgCdTe e-APD for near-IR gated-active/passive imaging. Specifically a 128 × 128 focal-plane
array (FPA) composed of 40-μm-pitch MWIR cutoff APD detectors and custom readout integrated circuit was designed, fabricated, and tested. Median gains
as high as 946 at 11 V bias with noise equivalent photon inputs as low as 0.4 photon were measured at 80 K and 1 μs gate times. This subphoton sensitivity is consistent with the high gains, low excess noise factor, and low effective gain
normalized dark-current densities, near or below 1 nA/cm2, that were achieved in these FPAs. A gated imaging demonstration system was designed and built using commercially available
parts. High resolution and precision gating was demonstrated in this system by imagery taken at ranges out to 9 km. 相似文献
3.
Johan Rothman Gwladys Perrais Philippe Ballet L. Mollard S. Gout J.-P. Chamonal 《Journal of Electronic Materials》2008,37(9):1303-1310
In this communication, we report on the electro-optical characterization of planar back-side-illuminated HgCdTe electron initiated
avalanche photodiode (e-APD) test arrays with cut-off wavelengths λ
c = 2.4 μm, λ
c = 4.8 μm, and λ
c = 9.2 μm. The e-APDs were manufactured at LETI using absorption layers grown by molecular beam epitaxy (MBE). We present measurements
of the distributions in gain, noise, and equivalent input dark current. The mid-wave (MW) diodes yielded a very low dispersion
(2%) and high operability (98%) for gains up to M = 200. The excess noise factor and equivalent input current (I
eq_in) operability were slightly lower, due to defects in the depletion region. The lowest measured value of I
eq_in = 1 fA corresponds to the lowest level measured so far in HgCdTe e-APDs and opens the way to new applications. The gain in
the long-wave (LW) diodes was limited by tunnelling currents to a value of M = 2.4, associated with an average noise factor F = 1.2. A gain of M = 20 at a bias of −22.5 V was demonstrated in the short-wave (SW) e-APDs. 相似文献
4.
S. Derelle S. Bernhardt R. Haidar J. Deschamps J. Primot J. Rothman S. Rommeluere N. Guérineau 《Journal of Electronic Materials》2009,38(8):1628-1636
We evaluated the performance of long-wavelength infrared (LWIR, λ
c = 9.0 μm at 80 K) mercury cadmium telluride electron-injected avalanche photodiodes (e-APDs) in terms of gain, excess noise factor,
and dark current, and also spectral and spatial response at zero bias. We found an exponential gain curve up to 23 at 100 K
and a low excess noise factor close to unity (F = 1–1.25). These properties are indicative of a single carrier multiplication process, which is electron impact ionization.
The dark current is prevailed by a diffusion current at low reverse bias. However, tunneling currents at higher reverse bias
limited the usable gain. The measurements of the pixel spatial response showed that the collection width, and, especially,
the amplitude of the response peak, increased with temperature. Furthermore, we developed a Monte Carlo model to understand
the multiplication process in HgCdTe APDs. The first simulation results corroborated experimental measurements of gain and
excess noise factor in mid-wavelength infrared (MWIR, x = 0.3) and LWIR (x = 0.235) e-APDs at 80 K. This model makes it possible for phenomenological studies to be performed to identify the main physical
effects and technological parameters that influence the gain and excess noise. The study of the effect of the n
−-layer thickness on APD performance demonstrated the existence of an optimum value in terms of gain. 相似文献
5.
P.Y. Emelie S. Velicu C.H. Grein J.D. Phillips P.S. Wijewarnasuriya N.K. Dhar 《Journal of Electronic Materials》2008,37(9):1362-1368
The general approach and effects of nonequilibrium operation of Auger-suppressed HgCdTe infrared photodiodes are well understood.
However, the complex relationships of carrier generation and dependencies on nonuniform carrier profiles in the device prevent
the development of simplistic analytical device models with acceptable accuracy. In this work, finite element methods are
used to obtain self-consistent steady-state solutions of Poisson’s equation and the carrier continuity equations. Experimental
current–voltage characteristics between 120 K and 300 K of HgCdTe Auger-suppressed photodiodes with cutoff wavelength of λ
c = 10 μm at 120 K are fitted using our numerical model. Based on this fitting, we study the lifetime in the absorber region, extract
the current mechanisms limiting the dark current in these photodiodes, and discuss design and fabrication considerations in
order to optimize future HgCdTe Auger-suppressed photodiodes. 相似文献
6.
Effect of Dislocations on VLWIR HgCdTe Photodiodes 总被引:5,自引:0,他引:5
T. Parodos E.A. Fitzgerald A. Caster S. Tobin J. Marciniec J. Welsch A. Hairston P. Lamarre J. Riendeau B. Woodward S. Hu M. Reine P. Lovecchio 《Journal of Electronic Materials》2007,36(8):1068-1076
The effects of dislocations on very-long-wavelength infrared (VLWIR) HgCdTe photodiodes (cutoff wavelength >14 μm at 40 K) have been determined experimentally and analyzed. The photodiodes are in the back-illuminated configuration, fabricated from HgCdTe p-on-n double-layer heterostructure (DLHJ) films grown at BAE Systems by liquid phase epitaxy (LPE) onto lattice-matched (111) CdZnTe substrates. Arrays were hybridized to silicon ROICs to form focal plane arrays (FPAs). After characterization for dark current and response, the arrays were dehybridized and stripped of their metals and passivation layers. Dislocations were revealed using a Hähnert and Schenk (H&;S) etch. Pixel traceability was maintained throughout the analysis, permitting one-to-one correlation between photodiode performance and dislocation density measured within that photodiode. We found that response and dark current were correlated to etch pit density (EPD), which we assumed to be equal to dislocation density. Our results support earlier dislocation studies on larger-bandgap HgCdTe, which showed response was only weakly impacted by EPD, while dark current was strongly affected by EPD. Measured EPD values ranged from low 105 to low 107 cm?2. Potential causes for this range in EPD are discussed. 相似文献
7.
J. Beck C. Wan M. Kinch J. Robinson P. Mitra R. Scritchfield F. Ma J. Campbell 《Journal of Electronic Materials》2006,35(6):1166-1173
Electron injection avalanche photodiodes in short-wave infrared (SWIR) to long-wave infrared (LWIR) HgCdTe show gain and excess
noise properties indicative of a single ionizing carrier gain process. The result is an electron avalanche photodiode (EAPD)
with “ideal” APD characteristics including near noiseless gain. This paper reports results obtained on long-, mid-, and short-wave
cutoff infrared Hg1−xCdxTe EAPDs (10 μm, 5 μm, and 2.2 μm) that use a cylindrical “p-around-n” front side illuminated n+/n-/p geometry that favors
electron injection into the gain region. These devices are characterized by a uniform, exponential, gain voltage characteristic
that is consistent with a hole-to-electron ionization coefficient ratio, k=αh/αe, of zero. Gains of greater than 1,000 have been measured in MWIR EAPDS without any sign of avalanche breakdown. Excess noise
measurements on midwave infrared (MWIR) and SWIR EAPDs show a gain independent excess noise factor at high gains that has
a limiting value less than 2. At 77 K, 4.3-μm cutoff devices show excess noise factors of close to unity out to gains of 1,000.
A noise equivalent input of 7.5 photons at a 10-ns pulsed signal gain of 964 measured on an MWIR APD at 77 K provides an indication
of the capability of this new device. The excess noise factor at room temperature on SWIR EAPDs, while still consistent with
the k=0 operation, approaches a gain independent limiting value of just under 2 because of electron-phonon interactions expected
at room temperature. The k=0 operation is explained by the band structure of the HgCdTe. Monte Carlo modeling based on the
band structure and scattering models for HgCdTe predict the measured gain and excess noise behavior. 相似文献
8.
Michael A. Kinch 《Journal of Electronic Materials》2008,37(9):1453-1459
A ballistic model is presented for electron avalanche multiplication in the conduction band of HgCdTe, based upon the concept
of an optical phonon limited mean free path for the electron, λ
e. The model predicts avalanche gain as a function of applied bias voltage V, and a threshold voltage for impact ionization V
th. Impact ionization probabilities are calculated analytically using a simplified band structure model for HgCdTe and used
to estimate values for the threshold energy for impact ionization. A simple ballistic model is developed to correlate the
relationship between electron energy and applied bias voltage, based upon the relevant electron scattering mechanisms in HgCdTe.
A comparison with published gain–voltage data suggests that the process is limited by optical phonon scattering, and the relationship
between electron energy and applied bias voltage, for a uniform electric field F = V/W, across a diode depletion width W, is given by E = α(E)V, where α(E) = [λ
e(E)/W]. For high electron energies λ
e(E) is independent of E and α(E) depends only on the dielectric parameters of the material. Using this simple model it is easy to predict electron avalanche
gain versus voltage for any parametric combination of diode geometry, bandgap, and operating temperature. 相似文献
9.
A few years ago, visible detection was demonstrated using advanced substrate thinning processes on flip-chip hybridized HgCdTe
focal-plane arrays, in both French and US laboratories. Constant quantum efficiency was demonstrated at LETI-Sofradir from
the short-wave infrared (IR) (2.5 μm cut-off) down to the visible range in 2006, validating complete CdZnTe substrate removal. This paper presents and discusses
HgCdTe photodiode spectral response characterization, focusing on the short-wavelength part of the spectrum. We confirm the
extended sensitivity of middle- and long-wave diodes: constant quantum efficiency has been observed from 10 μm down to 230 nm in the ultraviolet (UV). Such a unique property may be useful for very large-bandwidth spectrometers requiring
monolithic detectors. Avalanche gain of middle-wave avalanche photodiodes has also been investigated in both the visible and
the UV range. We demonstrate here that the avalanche gain remains constant while keeping a very low excess noise factor. This
result opens the way to low-flux applications in this wavelength range. 相似文献
10.
Jeffrey Beck Richard Scritchfield Billy Sullivan Jamie Teherani Chang-Feng Wan Mike Kinch Martha Ohlson Mark Skokan Lewis Wood Pradip Mitra Mike Goodwin Jim Robinson 《Journal of Electronic Materials》2009,38(8):1579-1592
The operation of the mid-wave infrared (MWIR) HgCdTe cylindrical electron injection avalanche photodiode (e-APD) is described.
The measured gain and excess noise factor are related to the collection region fill factor. A two-dimensional diffusion model
calculates the time-dependent response and steady-state pixel point spread function for cylindrical diodes, and predicts bandwidths
near 1 GHz for small geometries. A 2 μm diameter spot scan system was developed for point spread function and crosstalk measurements at 80 K. An electron diffusion
length of 13.4 μm was extracted from spot scan data. Bandwidth data are shown that indicate bandwidths in excess of 300 MHz for small unit
cells geometries. Dark current data, at high gain levels, indicate an effective gain normalized dark density count as low
as 1000 counts/μs/cm2 at an APD gain of 444. A junction doping profile was determined from capacitance–voltage data. Spectral response data shows
a gain-independent characteristic. 相似文献
11.
O. Gravrand E. De Borniol S. Bisotto L. Mollard G. Destefanis 《Journal of Electronic Materials》2007,36(8):981-987
This paper aims at studying the feasibility of very long infrared wavelength (VLWIR) (12–18 μm) focal plane arrays using n-on-p planar ion-implanted technology. To explore and analyze the feasibility of such VLWIR detectors, a set of four Cd
x
Hg1−x
Te LPE layers with an 18 μ cutoff at 50 K has been processed at Defir (LETI/LIR–Sofradir joint laboratory), using both our “standard” n-on-p process and our improved low dark current process. Several 320 × 256 arrays, 30-μm pitch, have been hybridized on standard Sofradir readout circuits and tested. Small dimension test arrays characterization
is also presented. Measured photonic currents with a 20°C black body suggest an internal quantum efficiency above 50%. Typical
I(V) curves and thermal evolution of the saturation current are discussed, showing that standard photodiodes remain diffusion
limited at low biases for temperatures down to 30 K. Moreover, the dark current gain brought by the improved process is clearly
visible for temperatures higher than 40 K. Noise measurements are also discussed showing that a very large majority of detectors
appeared background limited under usual illumination and biases. In our opinion, such results demonstrate the feasibility
of high-performance complex focal plane arrays in the VLWIR range at medium term. 相似文献
12.
Independently accessed back-to-back HgCdTe photodiodes: A new dual-band infrared detector 总被引:3,自引:0,他引:3
M. B. Reine P. W. Norton R. Starr M. H. Weiler M. Kestigian B. L. Musicant P. Mitra T. Schimert F. C. Case Lb. Bhat H. Ehsani V. Rao 《Journal of Electronic Materials》1995,24(5):669-679
We report the first data for a new two-color HgCdTe infrared detector for use in large dual-band infrared focal plane arrays
(IRFPAs). Referred to as the independently accessed back-to-back photodiode structure, this novel dual-band HgCdTe detector
provides independent electrical access to each of two spatially collocated back-to-back HgCdTe photodiodes so that true simultaneous
and independent detection of medium wavelength (MW, 3–5 μm) and long wavelength (LW, 8–12 μm) infrared radiation can be accomplished.
This new dual-band detector is directly compatible with standard backside-illuminated bump-interconnected hybrid HgCdTe IRFPA
technology. It is capable of high fill factor, and allows high quantum efficiency and BLIP sensitivity to be realized in both
the MW and LW photodiodes. We report data that demonstrate experimentally the key features of this new dual-band detector.
These arrays have a unit cell size of 100 x 100 μm2, and were fabricated from a four-layer p-n-N-P HgCdTe film grown in situ by metalorganic chemical vapor deposition on a CdZnTe
substrate. At 80K, the MW detector cutoff wavelength is 4.5 μm and the LW detector cutoff wavelength is 8.0 μm. Spectral crosstalk
is less than 3%. Data confirm that the MW and LW photodiodes are electrically and radiometrically independent. 相似文献
13.
Extrinsic p-type doping during molecular-beam epitaxy (MBE) growth represents an essential generic toolbox for advanced heterostructures
based on the HgCdTe material system: PiN diodes, mesa avalanche photodiodes (APD) or third-generation multispectral focal-plane
arrays. Today, arsenic appears to be the best candidate to fulfill this role and our group is actively working on its incorporation
during MBE growth, using an original radio frequency (RF) plasma source for arsenic. Such a cell is supposed to deliver a
monatomic As flux, and as expected we observed high As electrical activation rates after annealing short-wave (SW), mid-wave
(MW), and long-wave (LW) layers. At last, a couple of technological runs have been carried out in the MW range in order to
validate the approach on practical devices. p-on-n focal-plane arrays (FPA) have been fabricated using a mesa delineated technology on an As-on-In doped metallurgical heterojunction
layer grown on a lattice-matched CdZnTe layer (320 × 256, 30 μm pitch, 5 μm cutoff at 77 K). Observed diodes exhibit very interesting electro-optical characteristics: large shunt impedance, high quantum
efficiency, and no noticeable excess noise. The resulting focal-plane arrays were observed to be very uniform, leading to
high operabilities. Noise equivalent temperature difference (NETD) distributions are very similar to those observed with the
As ion-implanted p-on-n technology, fabricated in our laboratory as well. In our opinion, those excellent results demonstrate the feasibility of
our MBE in situ arsenic doping process. Good electrical activation rates and high-quality layers can be obtained. We believe that such an
approach allows precise control of the p-doping profile in the HgCdTe layer, which is necessary for advanced structure designs. 相似文献
14.
E. P. G. Smith G. M. Venzor A. M. Gallagher M. Reddy J. M. Peterson D. D. Lofgreen J. E. Randolph 《Journal of Electronic Materials》2011,40(8):1630-1636
Raytheon Vision Systems (RVS) continues to further its capability to deliver state-of-the-art high-performance, large-format,
HgCdTe focal-plane arrays (FPAs) for dual-band long-wavelength infrared (L/LWIR) detection. Specific improvements have recently
been implemented at RVS in molecular-beam epitaxy (MBE) growth and wafer fabrication and are reported in this paper. The aim
of the improvements is to establish producible processes for 512 × 512 30-μm-unit-cell L/LWIR FPAs, which has resulted in: the growth of triple-layer heterojunction (TLHJ) HgCdTe back-to-back photodiode
detector designs on 6 cm × 6 cm CdZnTe substrates with 300-K Fourier-transform infrared (FTIR) cutoff wavelength uniformity
of ±0.1 μm across the entire wafer; demonstration of detector dark-current performance for the longer-wavelength detector band approaching
that of single-color liquid-phase epitaxy (LPE) LWIR detectors; and uniform, high-operability, 512 × 512 30-μm-unit-cell FPA performance in both LWIR bands. 相似文献
15.
Low-Noise Mid-Wavelength Infrared Avalanche Photodiodes 总被引:1,自引:0,他引:1
Siddhartha Ghosh Shubhrangshu Mallick Koushik Banerjee Christoph Grein Silviu Velicu Jun Zhao Don Silversmith Jean Baptist Rodriguez Elena Plis Sanjay Krishna 《Journal of Electronic Materials》2008,37(12):1764-1769
Mid-wavelength infrared (MWIR) p
+–n
−–n
+ avalanche photodiodes (APDs) were fabricated using two materials systems, one with mercury cadmium telluride (HgCdTe) on
a silicon (Si) substrate and the other with an indium arsenide/gallium antimonide (InAs/GaSb) strained layer superlattice
(SLS). Diode characteristics, avalanche characteristics, and excess noise factors were measured for both sets of devices.
Maximum zero-bias resistance times active area (R
0
A) of 3 × 106 Ω cm2 and 1.1 × 106 Ω cm2 and maximum multiplication gains of 1250 at −10 V and 1800 at −20 V were measured for the HgCdTe and the SLS, respectively,
at 77 K. Gains reduce to 200 in either case at 120 K. Excess noise factors were almost constant with increasing gain and were
measured in the range of 1 to 1.2. 相似文献
16.
A. Sieck M. Benecke D. Eich R. Oelmaier J. Wendler H. Figgemeier 《Journal of Electronic Materials》2018,47(10):5705-5714
Short-wave infrared (SWIR) HgCdTe electron avalanche photodiodes (eAPDs) with different doping profiles have been characterized for use in SWIR gated viewing systems. Gated viewing offers enhanced image contrast in scenes with clutter from the foreground or background. HgCdTe-based eAPDs show exponential gain–voltage characteristics and low excess noise and are, therefore, well suited for active imaging applications. The gain achievable at a fixed reverse voltage varies with the bandgap of the Hg1?xCdxTe detector material. We analyze current–voltage and gain–voltage plots measured on SWIR Hg1?xCdxTe eAPDs with x?=?0.45, corresponding to a cutoff wavelength of 2.55 μm at 150 K. The cutoff has been chosen as a trade-off between achievable APD gain and operating temperature for SWIR gated-viewing systems with target distances of about 1000 m. Focal plane arrays with a readout-integrated circuit featuring a fast internal clock have been built and their performance with respect to gated viewing applications has been evaluated on a laboratory demonstrator for short distances. Future plans for a field demonstrator for distances up to 1000 m are described briefly at the end. 相似文献
17.
Gwladys Perrais Olivier Gravrand Jacques Baylet Gerard Destefanis Johan Rothman 《Journal of Electronic Materials》2007,36(8):963-970
HgCdTe midwave infrared pin avalanche photodiodes (APDs) have been studied as a function of temperature and bias, for two types of junction profiles
with different nominal junction width and the same cut-off wavelength λc = 5.0 μm at T = 77 K. A gain of 5,300 at a reverse bias of 12.5 V was demonstrated in the nominally wide junction pin-APD at T = 77 K. The nominally narrow pin-APD showed a higher gain at low bias, but the maximum gain was lower due to an earlier onset of excess currents. The gain
was measured for temperatures (T) between 30 K and 150 K and was found to decrease with increasing temperatures, in correlation with the increase in band
gap. However, the useful gain was reduced at lower temperatures, due to increased excess current at high reverse bias, indicating
a tunnel limited origin of the sensitivity limiting excess current. The noise factor, F, showed a nearly deterministic multiplication of the carriers, with F = 1–1.5 up to gains of 5,000. 相似文献
18.
P. Mitra F. C. Case H. L. Glass V. M. Speziale J. P. Flint S. P. Tobin P. W. Norton 《Journal of Electronic Materials》2001,30(6):779-784
We report the growth of HgCdTe on (552)B CdZnTe by metalorganic vapor phase epitaxy (MOVPE). The (552) plane is obtained by
180 rotation of the (211) plane about the [111] twist axis. Both are 19.47 degrees from (111), but in opposite directions.
HgCdTe grown on the (552)B-oriented CdZnTe has a growth rate similar to the (211)B, but the surface morphology is very different.
The (552)B films exhibit no void defects, but do exhibit ∼40 μm size hillocks at densities of 10–50 cm−2. The hillocks, however, are significantly flatter and shorter than those observed on (100) metalorganic vapor phase epitaxy
(MOVPE) HgCdTe films. For a 12–14 μm thick film the height of the highest point on the hillock is less than 0.75 μm. No twinning
was observed by back-reflection Laue x-ray diffraction for (552)B HgCdTe films and the x-ray double crystal rocking curve
widths are comparable to those obtained on (211)B films grown side-by-side and with similar alloy composition. Etch pit density
(EPD) measurements show EPD values in the range of (0.6–5)×105 cm−2, again very similar to those currently observed in (211)B MOVPE HgCdTe. The transport properties and ease of dopant incorporation
and activation are all comparable to those obtained in (211)B HgCdTe. Mid-wave infrared (MWIR) photodiode detector arrays
were fabricated on (552)B HgCdTe films grown in the P-n-N device configuration (upper case denotes layers with wider bandgaps).
Radiometric characterization at T=120–160 K show that the detectors have classical spectral response with a cutoff wavelength
of 5.22 μm at 120 K, quantum efficiency ∼78%, and diffusion current is the dominant dark current mechanism near zero bias
voltage. Overall, the results suggest that (552)B may be the preferred orientation for MOVPE growth of HgCdTe on CdZnTe to
achieve improved operability in focal plane arrays. 相似文献
19.
Johan Rothman G. Vojetta B. Moselle L. Mollard S. Gout J.-P. Chamonal 《Journal of Electronic Materials》2010,39(7):837-845
A combined study of the avalanche gain characteristics of HgCdTe electron-avalanche photodiodes (e-APDs) and of the minority
electron properties in the p-type absorber using Shockley–Haynes (SH) measurements is presented for various Cd compositions x
Cd. Ideal gain performance associated with a low excess noise factor F = 1.2 have been measured at T = 80 K down to cutoff wavelengths of λ
c = 2.9 μm. The observation of both a record high, exponentially increasing gain of M = 600 in short-wave e-APDs and a low excess noise factor proved that the exclusive electron multiplication is stable down
to x
Cd = 0.4. Zero-flux measurements at 80 K confirmed that the dark current tends to decrease at constant gain as x
Cd increases. Measurements using a readout integrated circuit allowed us to establish a new record in sensitivity for APDs:
I
eq_in = 2 aA, corresponding to 12 e/s at gain of M = 24 in an e-APD with λ
c = 2.9 μm. SH measurements enabled direct estimation of the electron diffusion coefficient, drift velocity, and lifetime in the p-type absorber of the e-APDs as a function of electric field at temperatures between 80 K and 200 K. Measurements at 80 K
yielded lifetimes consistent with the values expected for the nominal doping of the samples. The low-field electron drift
mobility, estimated from the drift velocity, was found to be a factor of 0.4 to 0.5 lower than the mobility in n-type material with the same composition. In mid-wave (MW) infrared samples with λ
c = 5.3 μm, the mobility was observed to be μ
ep = 15 kcm2/Vs to 20 kcm2/Vs, being less than μ
en ≈ 40 kcm2/Vs to 50 kcm2/Vs. The reduction in mobility can, in part, be attributed to scattering by ionized acceptors and heavy holes. The diffusion
mobility, estimated from the diffusion coefficient, was systematically higher than the drift mobility, indicating diffusion
of hot electrons with a temperature higher than that of the lattice. The saturation velocity, v
sat_ep = 2 × 106 cm/s to 6 × 106 cm/s, did not correlate with the Cd composition in the samples. The measured saturation velocities made it possible to estimate
the timing jitter in p-type absorbers with a built-in electric field. Jitter below 100 ps was estimated for SW and MW APDs with absorbing layer
thicknesses up to 4 μm. 相似文献
20.
HgCdTe electron avalanche photodiodes 总被引:1,自引:0,他引:1
M. A. Kinch J. D. Beck C. -F. Wan F. Ma J. Campbell 《Journal of Electronic Materials》2004,33(6):630-639
Exponential-gain values well in excess of 1,000 have been obtained in HgCdTe high-density, vertically integrated photodiode
(HDVIP) avalanche photodiodes (APDs) with essentially zero excess noise. This phenomenon has been observed at temperatures
in the range of 77–260 K for a variety of cutoff wavelengths in the mid-wavelength infrared (MWIR) band, with evidence of
similar behavior in other IR bands. A theory for electron avalanche multiplication has been developed using density of states
and electron-interaction matrix elements associated with the unique band structure of HgCdTe, with allowances being made for
the relevant scattering mechanisms of both electrons and holes at these temperatures. This theory is used to develop an empirical
model to fit the experimental data obtained at DRS Infrared Technologies. The functional dependence of gain on applied bias
voltage is obtained by the use of one adjustable parameter relating electron energy to applied voltage. A more quantitative
physical theory requires the use of Monte Carlo techniques incorporating the preceding scattering rates and ionization probabilities.
This has been performed at the University of Texas at Austin, and preliminary data indicate good agreement with DRS models
for both avalanche gain and excess noise as a function of applied bias. These data are discussed with a view to applications
at a variety of wavelengths. 相似文献