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1.
There has been recent experimental evidence that showed, in heavily doped p-type HgCdTe, the lifetime may be limited by the
Auger 7 recombination mechanism. We have performed a detailed calculation of both the Auger 7 and Auger 1 lifetimes as a function
of Cd composition (x), temperature (T), and doping (NA). Compared with those done 20 years ago, the depth and breadth of these calculations result in a significant increase in
the accuracy of the predictions. We present here the Auguer 7 lifetime for two different compositions, x=0.305 and x=0.226
over a range of temperature extending from 60 K to 300 K and for acceptor doping from 1015 cm−3 to 1018 cm−3. The calculated results for MWIR (x=0.305) are in reasonably good agreement with recent experiments performed on MWIR HgCdTe
at 77 K over a range of doping. In addition, we calculated γ (≡ τA7 /τA1) with the same doping, composition (x ≈ 0.22), for a range of temperatures (40–80 K) and found γ=3–6. 相似文献
2.
Measurement of minority carrier lifetime in n-type MBE HgCdTe and its dependence on annealing 总被引:1,自引:0,他引:1
D. D. Edwall R. E. DeWames W. V. McLevige J. G. Pasko J. M. Arias 《Journal of Electronic Materials》1998,27(6):698-702
Results are presented for minority carrier lifetime in n-type molecular beam epitaxy Hg1−xCdxTe with x ranging from 0.2 to 0.6. It was found that the lifetime was unintentionally degraded by post-growth annealing under
Hg saturated conditions in a H2 atmosphere that was both time and temperature dependent. This effect was minimal or non-existent for x∼0.2 material, but
very strong for x ≥ 0.3. Hydrogen was identified as responsible for this degradation. Identical annealing in a He atmosphere
avoids this degradation and results in neartheoretical lifetime values for carrier concentrations as low 1 × 1015 cm−3 in ≥0.3 material. Modeling was carried out for x∼0.2 and x∼0.4 material that shows the extent to which lifetime is reduced
by Shockley-Real-Hall recombination for carrier concentrations below 1 × 1015 cm−3, as well as for layers annealed in H2. It appears that annealing in H2 results in a deep recombination center in wider bandgap HgCdTe that lowers the lifetime without affecting the majority carrier
concentration and mobility. 相似文献
3.
Silver doped p-type Mg2Ge thin films were grown in situ at 773 K using magnetron co-sputtering from individual high-purity Mg and Ge targets. A sacrificial
base layer of silver of various thicknesses from 4 nm to 20 nm was initially deposited onto the substrate to supply Ag atoms,
which entered the growing Mg2Ge films by thermal diffusion. The addition of silver during film growth led to increased grain size and surface microroughness.
The carrier concentration increased from 1.9 × 1018 cm−3 for undoped films to 8.8 × 1018 cm−3 for the most heavily doped films, but it did not reach saturation. Measurements in the temperature range of T = 200–650 K showed a positive Seebeck coefficient for all the films, with maximum values at temperatures between 400 K and
500 K. The highest Seebeck coefficient of the undoped film was 400 μV K−1, while it was 280 μV K−1 for the most heavily doped film at ∼400 K. The electrical conductivity increased with silver doping by a factor of approximately
10. The temperature effects on power factors for the undoped and lightly doped films were very limited, while the effects
for the heavily doped films were substantial. The power factor of the heavily doped films reached a non-optimum value of ∼10−5 W cm−1 K−2 at 700 K. 相似文献
4.
R. Sewell C. A. Musca J. M. Dell L. Faraone K. Józwikowski A. Rogalski 《Journal of Electronic Materials》2003,32(7):639-645
The steady-state lifetime of photogenerated minority carriers has been investigated in heterostructure HgCdTe devices fabricated
on molecular-beam epitaxy (MBE) grown material. A wider bandgap capping layer (Hg(1−x)Cd(x)Te, x = 0.44) was grown on a narrower bandgap absorbing layer (Hg(1−x)Cd(x)Te, x = 0.32, λco,80K = 4.57 μm) material in an uninterrupted MBE growth to create an abrupt heterointerface. Steady-state lifetime as a function
of temperature over the range 80–300 K was extracted from photoconductive responsivity at an optical wavelength corresponding
to the peak responsivity at that temperature. At 80 K, the photoconductors exhibit a specific detectivity of 4.5 × 1011 cm Hz−1/2W−1 (chopping frequency of 1 kHz). For each measurement temperature, the steady-state excess carrier lifetime determined experimentally
was compared to the theoretical bulk lifetime for material with x = 0.32 and effective n-type doping density of 3.7 × 1014 cm−3. Theoretical calculations of the Auger-1 lifetime based on expressions developed by Pratt et al. were not able to account
for the reduction in lifetime observed at temperatures above 180 K. Two approaches have been attempted to resolve this discrepancy:
A semiempirical expression for Auger lifetime attributed to Meyer et al. was used to fit to the data, with the Auger coefficient
γ as a fitting parameter. However, the resulting Auger coefficient found in this work is more than an order of magnitude higher
than that reported previously. Alternatively, the reduction in effective lifetime above 180 K may be understood as a “loss”
of carriers from the narrow bandgap absorbing layer that are promoted across the potential barrier in the conduction band
into a low lifetime, wider bandgap capping layer. The reduction in lifetime as a function of inverse temperature for temperatures
above 180 K may be fitted by a “cap lifetime” that has an activation energy equal to the change in bandgap across the heterostucture
and scaled by a fitting constant. 相似文献
5.
M. Tanaka K. Ozaki H. Nishino H. Ebe Y. Miyamoto 《Journal of Electronic Materials》1998,27(6):579-582
We employed AgNO3 solutions for doping Ag in liquid phase epitaxy (LPE) grown Hg0.78Cd0.22Te epilayers and found that the minority carrier lifetimes became longer so that the diode properties improved. After annealing
LPE grown Hg(1-x)Cd(x)Te layers (x=0.22) in Hg atmosphere, the epilayers were immersed in an AgNO3 solution at room temperature. The typical carrier concentrations of holes was 3 × 1016 cm−3 at 77K. These values were almost the same as for the nondoped wafers. Also, its acceptor level was 3 to 4 meV. This shows
that the Ag was activated. The doped crystals have lifetimes several times longer than those of the nondoped crystals. Numerical
fitting showed the lifetime was limited mostly by the Auger 7 process. The Shockley-Read-Hall recombination process was not
effective. To examine the Ag-doped wafer, we fabricated photodiodes using standard planar technology. The diodes have an average
zero-bias resistance of several MΩ and a shunt resistance of about 1 GΩ for a 10 μm cutoff wavelength at 78K. These values
are about four times higher than those of nondoped diodes. The photo current is also two times higher at the same pixel size.
This shows that the quantum efficiency is increased. The extension of the lifetime contributes to the high resistance and
the high quantum efficiency of the photodiode. 相似文献
6.
P. S. Wijewarnasuriya M. D. Lange S. Sivananthan J. P. Faurie 《Journal of Electronic Materials》1995,24(5):545-549
We have studied the minority-carrier lifetime on intentionally indium-doped (211)B molecular beam epitaxially grown Hg1-xCdxTe epilayers down to 80K with x ≈ 23.0% ± 2.0%. Measured lifetimes were explained by an Auger-limited band-to-band recombination
process in this material even in the extrinsic temperature region. Layers show excellent electron mobilities as high as ≈2
x 105 cm2v-1s-1 at low temperatures. When the layers are compensated with Hg vacancies, results show that the Schockley-Read recombination
process becomes important in addition to the band-to-band processes. From the values of τn0 and τp0 of one sample, the obtained defect level is acceptor-like and is somewhat related to the Hg vacancies. 相似文献
7.
D. Chandra H. F. Schaake J. H. Tregilgas F. Aqariden M. A. Kinch A. J. Syllaios 《Journal of Electronic Materials》2000,29(6):729-731
Measurements have been performed of the carrier concentrations in vacancy-doped Hg1−xCdxTe with x=0.22, 0.29, 0.45, and 0.5. Anneals to establish the carrier concentrations were performed on both the mercury- and
tellurium-rich sides of the phase field. When these results were added to earlier data for x=0.2 and 0.4, and assuming that
all vacancies are doubly ionized, then vacancy concentrations for all values of x and anneal temperature can be represented
by simple equations. On the mercury side of the phase field, the vacancy concentrations varied as 2.50×1023(1−x) exp[−1.00/kT] for low concentrations, and as 3.97×107(1−x)1/3n
i
2/3
exp[−0.33/kT] for high concentrations, where ni is the intrinsic carrier concentration. On the tellurium rich side, the vacancy concentrations varied as 2.81 × 1022(1−x) exp[−0.65/kT] for low concentrations and as 1.92×107(1−x)1/3n
i
2/3
exp[−0.22/kT] for high concentrations. 相似文献
8.
《Materials Science in Semiconductor Processing》2012,15(1):56-60
We have investigated the extended phosphorus diffusion gettering (PDG) effect on chromium impurities (Cr) in p-type multicrystalline silicon (mc-Si) grown by Heat Exchanger Method (HEM). The study was made after phosphorous diffusion and according to different extended annealing temperatures. The secondary ion mass spectrometry (SIMS) analysis revealed a significant accumulation of 52Cr in heavily phosphorus doped (HPD) region. Using quasi-steady state photoconductance (QSSPC) technique, the apparent lifetime dependent minority carrier density curves have been obtained. The results showed an increment of the bulk minority carrier lifetime for specific annealing temperatures. Appropriate calculations based on QSSPC results allowed us to determine the lifetime curves associated to gettered impurities. Their fitting by Shockley-Read-Hall (SRH) model reveal that the origin of the lifetime increment is the reduction of interstitial chromium (Cri) density in the bulk. Furthermore, the estimation of electron to hole capture cross-section ratio (k=σn/σp) through the modelling of apparent lifetime curves using Hornbeck–Haynes model, confirmed the effectiveness of Cri gettering and identified the nature of dominant recombination centres after gettering process. 相似文献
9.
A. V. Voitsekhovskii Yu. A. Denisov A. P. Kokhanenko V. S. Varavin S. A. Dvoretskii V. T. Liberman N. N. Mikhailov Yu. G. Sidorov 《Semiconductors》1997,31(7):655-657
Measurements of the charge carrier lifetime in epitaxial structures based on narrow-gap Hg1−x
CdxTe (x=0.22), grown by molecular-beam epitaxy with pulsed excitation using radiation at different wavelengths, are reported. It
is shown that in p-type epitaxial films the lifetime is determined by the Auger recombination mechanism at temperatures corresponding to the
impurity conductivity, and for n-type epitaxial films recombination via local centers is characteristic.
Fiz. Tekh. Poluprovodn. 31, 774–776 (July 1997) 相似文献
10.
W. Taudt B. Wachtendorf F. Sauerländer H. Hamadeh S. Lampe M. Heuken 《Journal of Electronic Materials》1995,24(11):1671-1675
In a low-pressure metalorganic vapor phase epitaxy process, we used dc-plasma activated nitrogen to dope ZnSe, grown with
ditertiarybutylselenide and dimethylzinc-triethylamine. The nitrogen concentration of up to 2 × 1018 cm−3 in the doped layers can be adjusted by the growth temperature, the dc-plasma power, and the N2 dopant flow. Due to the high n-type background carrier concentration of the order of 1017 cm−3 in undoped samples, the doped layers show n-type conductivity or were semi-insulating because of an additional compensation
by hydrogen incorporated with a concentration of the order of 1018 cm−3. A planar doping scheme was applied to reduce this hydrogen incorporation by one order of magnitude, although H2 was used as carrier gas. 相似文献
11.
12.
Current-voltage characteristics of the In-ZnGa2Se4-In structure have been studied in the temperature range of 90–335 K. Based on the data calculated for the concentration of
three trap types in ZnGa2Se4, the values N
t
= 1.4 × 1013, 8.2 × 1012, and 2.6 × 1012 cm−3 are obtained. The contact region transparency D
k
*= 10−5, surface recombination velocity S
k
= 0.65 m/s, and carrier lifetime τ = 1.5 × 10−4 s were determined. It was found that the current transmission mechanism in electric fields weaker than 103 V/cm is caused by monopolar carrier injection. 相似文献
13.
Using a Schottky diode photocurrent technique, investigations have been made of the room temperature value of minority carrier diffusion length in liquid epitaxial GaP grown on both (111) and (100) oriented pulled GaP substrates. Results are presented for undoped layers and layers doped separately with S, S and N, Te, Zn, and Zn and O, to cover a range of impurity concentration in the GaP. The measured values of minority carrier diffusion length are found to depend on the concentration of the dominant impurity and, for the undoped and Zn doped layers, also on the growth orientation of the substrate. From the dependence of the minority carrier diffusion length on majority carrier concentration we infer the dominant room temperature recombination process in the layers. In our undoped layers this process is believed to correspond to recombination via residual Si substituted on P sites. In Te, S, Zn, and Zn, O doped layers the dominant recombination mechanism can be attributed to a non-radiative band-band Auger process, although in the case of the Zn, O doped layers a competing recombination process is observed which is believed to correspond to recombination via centres formed by unpaired O and Zn defects. The lifetime for this competing process is predicted to be sensitive to annealing. 相似文献
14.
On the basis of the self-consistent model of transport processes in the semiconductor p–i–n diode during its self-heating under conditions of limited heat sink, the mechanisms of unusual effect—the formations of
N–S transition in nonisothermal I–V characteristics of the device were numerically analyzed. It is established that such an effect is caused by a pronounced
temperature reduction of the mobility of carriers in the high-resistivity base and the injection-level saturation at the current
densities J > 300–500 A/cm2. The saturation is attained due to the Auger recombination or the leakage of carriers from plasma into heavily doped emitter
layers, the integrated current of which, as a rule, exceeds the recombination integrated current in the base under these conditions.
The Auger recombination in the anode emitter also starts to play an appreciable role in the injection-level restriction in
the base if the impurity concentration becomes higher than 1018 cm−3 in there. 相似文献
15.
Variable temperature Hall effect measurements have been made down to 9–10K on p-type Hg1−xCdxTe grown by liquid phase epitaxy on both CdTe and sapphire substrates. Carrier freeze-out was usually observed throughout
the measured temperature range. For most samples, the hole mobility was well-behaved and exhibited a maximum at ˜ 35K. Values
of acceptor ionization energy EA and donor concentration ND were estimated from the data, using a model assuming significant compensation, which provided a good fit to the low temperature
data. In addition, values of ND were also estimated from an analysis of the low temperature mobility using the hole effective mass as a parameter to provide
reasonable agreement between the ND values calculated from the Hall coefficient and mobility data. The measured carrier concentration is a result of close compensation
between stoichiometric acceptors and donors, with ND usually in the low-1017 cm−3 range. Average values of EA for as-grown, undoped x = 0.32 layers on CdTe and sapphire substrates are 7.4 and 6.6 meV, respectively. An activation energy
of 0.84 meV was determined for a Cu-doped x = 0.32 layer that was annealed in Hg vapor to reduce the number of Hg vacancies.
The average EA for undoped Hg-annealed x = 0.22 layers on CdTe substrates is 2.35 meV. Layers with x = 0.32 grown on sapphire substrates
have average carrier concentrations of 2.92 (σ = 0.54) × 1016 cm−3, compared with 4.64 (θ = 1.26) × 1016 cm−3 for the same composition layers grown on CdTe substrates. 相似文献
16.
Hwe Jae Lee Soon Jae Yu Hajime Asahi Shun-Ichi Gonda Young Hwan Kim Jin Koo Rhee S. J. Noh 《Journal of Electronic Materials》1998,27(7):829-832
Ohmic contacts with low resistance are fabricated on n-GaN films using Al/Ti bilayer metallization. GaN films used are 0.3
μm thick layers with carrier concentrations of 1 × 1019 cm−3 grown on the c-plane sapphire by ion-removed electron cyclotron resonance molecular beam epitaxy. The lowest value for the
specific contact resistivity (ρc) of 1.2×10−8 Ω·cm2 was obtained with furnace annealing at 500°C for 60 min. This result shows the effectiveness of high carrier concentration
GaN layers and the low temperature annealing for the realization of low resistance ohmic contacts. Sputtering Auger electron
spectroscopy analysis reveals that Al diffuses into Ti layer and comes into contact with the GaN surface. 相似文献
17.
Philip G. Neudeck 《Journal of Electronic Materials》1998,27(4):317-323
Minority carrier lifetimes in epitaxial 4H-SiC p+n junction diodes were measured via an analysis of reverse recovery switching characteristics. Behavior of reverse recovery
storage time (ts) as a function of initial ON-state forward current (IF) and OFF-state reverse current (IR) followed well-documented trends which have been observed for decades in silicon p+n rectifiers. Average minority carrier (hole) lifetimes (τp) calculated from plots of ts vs IR/IF strongly decreased with decreasing device area. Bulk and perimeter components of average hole lifetimes were separated by
plotting 1/τp as a function of device perimeter-to-area ratio (P/A). This plot reveals that perimeter recombination is dominant in these
devices, whose areas are all less than 1 mm2. The bulk minority carrier (hole) lifetime extracted from the 1/τp vs P/A plot is approximately 0.7 μs, well above the 60 ns to 300 ns average lifetimes obtained when perimeter recombination
effects are ignored in the analysis. Given the fact that there has been little previous investigation of bipolar diode and
transistor performance as a function of perimeter-to-area ratio, this work raises the possibility that perimeter recombination
may be partly responsible for poor effective minority carrier lifetimes and limited performance obtained in many previous
SiC bipolar junction devices. 相似文献
18.
Liquid-phase epitaxy is used to fabricate Pb0.8Sn0.2Te films, undoped or doped with indium to different levels. The depth profiles of the carrier density and dopant concentration
in the films are measured and examined. A uniform dopant concentration to a depth of 15 μm is obtained. Electrical-conduction
inversion is observed at a temperature of 77.3 K as the doping level is varied. The liquid-phase epitaxial method is shown
to be a more suitable technology for the reproducible manufacture of epitaxial films with a given carrier density, such as
the ones used in terahertz detectors. 相似文献
19.
G. W. Iseler 《Journal of Electronic Materials》1984,13(6):989-1011
By reducing the temperature gradients in the vicinity of the crystal-melt interface, 35-mm-diameter InP boules with much reduced
dislocation densities have been grown by the liquid-encapsulated Czochralski technique. A reduction in the residual donor
concentration of InP grown by this technique has been achieved by using In-rich charges prepared by adding elemental In to
polycrystalline InP ingot material. Nominally undoped crystals with carrier concentrations as low as 1–2 x4 1015 Cm − 1 and 77 K mobilities as high as 7.0 × 10 cm2 V−1 s−1 have been obtained. By growing doped crystals at increased seed or crucible rotation rates, short-range longitudinal variations
in dopant concentration have been reduced to a few per cent, as determined by optical absorption measurements with a scanning
CO2 laser. 相似文献
20.
S. Velicu G. Badano Y. Selamet C. H. Grein J. P. Faurie S. Sivananthan P. Boieriu Don Rafol R. Ashokan 《Journal of Electronic Materials》2001,30(6):711-716
Conventional HgCdTe infrared detectors need significant cooling in order to reduce noise and leakage currents resulting from
thermal generation and recombination processes. Although the need for cooling has long been thought to be fundamental and
inevitable, it has been recently suggested that Auger recombination and generation rates can be reduced by using the phenomena
of exclusion and extraction to produce nonequilibrium carrier distributions. The devices with Auger suppressed operation requires
precise control over the composition, and donor and acceptor doping. The successful development of the molecular beam epitaxy
(MBE) growth technique for multi-layer HgCdTe makes it possible to grow these device structures. Theoretical calculations
suggest that the p n+ layer sequence is preferable for near-room temperature operation due to longer minority carrier lifetime
in lightly doped p-HgCdTe absorber layers. However, because the low doping required for absorption and nonequilibrium operation
is easier to achieve in n-type materials, and because Shockley-Read centers should be minimized in order to obtain the benefits
of Auger suppression, we have focused on p+ n structures. Planar photodiodes were formed on CdTe/Si (211) composite substrates by As implantation followed by a three
step annealing sequence. Three inch diameter Si substrates were employed since they are of high quality, low cost, and available
in large areas. Due to this development, large area focal plane arrays (FPAs) operated at room temperature are possible in
the near future. The structures were characterized by FTIR, x-ray diffraction, temperature dependent Hall measurements, minority
carrier lifetimes by photoconductive decay, and in-situ ellipsometry. To study the relative influence of bulk and surface
effects, devices with active areas from 1.6 10−5 cm2 to 10−3 cm2 were fabricated. The smaller area devices show better performance in terms of reverse bias characteristics indicating that
the bulk quality could be further improved. At 80 K, the zero bias leakage current for a 40 m 40 m diode with 3.2 m cutoff
wavelength is 1 pA, the R0A product is 1.1 104-cm2 and the breakdown voltage is in excess of 500 mV. The device shows a responsivity of 1.3 107 V/W and a 80 K detectivity of 1.9 1011 cm-Hz1/2/W. At 200 K, the zero bias leakage current is 5 nA and the R0A product 2.03-cm2, while the breakdown voltage decreases to 40 mV. 相似文献