Design considerations for 1.06-/spl mu/m InGaAsP-InP Geiger-mode avalanche photodiodes

For Geiger-mode avalanche photodiodes, the two most important performance metrics for most applications are dark count rate (DCR) and photon detection efficiency (PDE). In 1.06-/spl mu/m separate-absorber-avalanche (multiplier) InP-based devices, the primary sources of dark counts are tunneling through defect levels in the InP avalanche region and thermal generation in the InGaAsP absorber region. PDE is the probability that a photon will be absorbed (quantum efficiency) times the probability that the electron-hole pair generated will actually cause an avalanche. A device model based on experimental data that can simultaneously predict DCR and PDE as a function of overbias and temperature is presented. This model has been found useful in predicting changes in performance as various device parameters, such as avalanche layer thickness, are modified. This has led to designs that are capable simultaneously of low DCR and high PDE.     

InP/InGaAs buried-structure avalanche photodiodes

Planar InP/InGaAs avalanche photodiodes with a new guardring structure have been designed and fabricated. The diodes had a buried n-InP layer and an n?-InP multiplication region under p-n junctions. A successful guardring effect was obtained. The diode exhibited a uniform multiplication over the active region, a maximum multiplication factor of 30, low dark currents of around 20 nA at 90% of breakdown voltage and a flat frequency response up to 1 GHz. Multiplication noise was measured up to a multiplication factor of 17.     

Photon counting with silicon avalanche photodiodes

Avalanche photodiodes (APDs) are studied for use as photon-counting detectors. The APD may be biased slightly above (Geiger mode) or slightly below its voltage breakdown point. In the latter case, if the photon absorption rate is low enough, each individual photoelectron current pulse may be resolved with the use of a discriminator. APDs used in this photon-counting mode are shown to give the best performance at low light levels. Experimentally, overall photon detection probabilities of 5.0 and 0.33% were obtained at λ=820 nm and λ=1.064 μm, respectively, with a photon counter dead time as low as 15 ns and a dark current counting rate of 7000/s. The APD photon counter exhibited an exponential photon interarrival time probability density and a near-Poissonian photon-counting probability     

InP/InGaAsP avalanche photodiodes with new guard ring structure

A new guard ring structure for InP/InGaAsP avalanche photodiodes is described, which makes use of the impurity concentration difference between two InP epitaxial layers. The guard ring effect gives a low dark current and uniform multiplication characteristics at ? = 1.29 ?m.     

InP-lnGaAsP planar avalanche photodiodes with self-guard-ring effect

Marked diode characteristics dependence on the distance between p-n junction and heterointerface in double heterojunction InP-InGaAsP planar a.p.d.s is described. In a diode with an optimised configuration, as high as 3000 maximum avalanche gain and less than 3×10?6 A/cm2 dark-current density at 0.9 VB are achieved.     

Epitaxial structures for InGaAs/InP avalanche photodiodes

The influence of parameters of the MOS hydride epitaxy on structural and electrophysical characteristics of InGaAs/InP heterostructures is studied experimentally. The chosen parameters are used to grow device structures and fabricate planar avalanche photodiodes based on them. The results of measuring of their photoelectrical properties suggest that the developed structures are suitable for fabrication of commercial planar avalanche photodiodes.     

A low voltage hybrid bulk/SOI CMOS active pixel image sensor

A hybrid bulk/silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) active pixel image sensor has been fabricated and studied. The active pixel comprised of reset and source follow transistors on the SOI thin film while the photodiode is fabricated on the SOI handling substrate after removing the buried oxide. The bulk photodiode can be optimized for efficiency with the use of lightly doped SOI substrate without compromising the circuit performance. On the other hand, the elimination of wells on the SOI thin-film allows the use of PMOSFET without increasing the pixel size. The addition of a PMOSFET in the active pixel structure can reduce the minimum operating voltage of the circuit beyond that of conventional designs. With the combination of the high quantum efficiency of bulk photodiode and the low power advantage of SOI technology, the hybrid technology is attractive for scaled low voltage imaging applications     

High-speed InP/InGaAs avalanche photodiodes with a compositionallygraded quaternary layer

InP/InGaAs avalanche photodiodes (APDs) with a compositionally graded quaternary layer at the heterointerface between the InGaAs absorption and InP multiplication regions were fabricated and tested. A comparison of samples with the graded layer and with conventional three quaternary layers showed that the frequency characteristics for samples with the graded layer did not deteriorate at a low bias voltage even below -100°C, unlike APDs with three InGaAsP layers. Thus, no hole trapping occurred at the InP/InGaAs heterointerface with the graded layer. A sample with the graded layer showed a cutoff frequency exceeding 9 GHz at a low multiplication factor of 2. The authors found InP/InGaAs APDs with the compositionally graded quaternary layer to be useful over a wide temperature range     

Frequency response of InP/InGaAsP/InGaAs avalanche photodiodes

A theoretical model for the frequency response of InP/InGaAs avalanche photodiodes (APDs) is presented. Included in the analysis are resistive, capacitive, and inductive parasitics, transit-time factors, hole trapping at the heterojunction interfaces, and the avalanche buildup time. The contributions of the primary electrons, primary holes, and secondary electrons to the transit-time-limited response are considered separately. Using a measurement apparatus which consists of a frequency synthesizer and a spectrum analyzer controlled by a microcomputer, the frequency response of InP/InGaAsP/InGaAs APDs grown by chemical-beam epitaxy are measured. Good agreement with the calculated response has been obtained over a wide range of gains     

High-gain GaAs avalanche photodiodes with proton-implanted guard ring

A GaAs avalanche photodiode with a multiplication factor as high as 8000 was prepared by Zn diffusion and proton double implantation. The proton-implanted guard ring completely prevented edge breakdown, and multiplication occurred uniformly over the junction area. Dark current was proved to be due to a leakage current at the periphery between junction and implanted layer.     

Vapour-grown 1.3 ?m InGaAsP/InP avalanche photodiodes

A novel planar InGaAsP/InP avalanche photodiode structure prepared by vapour-phase epitaxy is described. Avalanche gain up to 20 at 1.3 ?m and at reverse breakdown of 65 V has been measured.     

1.3 ?m InP/InGaAsP planar avalanche photodiodes

An InP/InGaAsP planar avalanche photodiode operating at a wavelength of 1.3 ?m has been fabricated by using Be implantation and a difference of impurity concentrations between two n-InP epitaxial layers. A sufficient guard ring effect is demonstrated by a photoresponse, and an avalanche gain of 110 is obtained at an initial photocurrent of 0.35 ?A.     

Double junction AlInAs/GaInAs multiquantum well avalanche photodiodes

A separate absorption, grading, and multiplication avalanche photodiode with an AlInAs/GaInAs multiquantum well multiplication region is reported. This device exhibits a low excess-noise factor and a gain-bandwidth product of 50 GHz, due to the high ratio of ionisation rates of the multiplication material. In addition, a large bandwidth is obtained owing to the use of an undoped (n type) GaInAs absorption layer, fully depleted when multiplication occurs.<>     

Planar InP/InGaAs avalanche photodiodes with preferential lateral extended guard ring

High-speed and high-sensitivity planar InP/InGaAs avalanche photodiodes (APD's) have been fabricated with a newly developed preferential lateral extended guard ring (PLEG). By employing the configuration, avalanche photodiode yield was markedly improved without edge breakdown. Received powers required to give 10^-9bit-error rate (BER) at 1.55-1.57-µm wavelength were -44.5 and -37.4 dBm for 450 Mbit/s and 2 Gbit/s, respectively.     

Liquid-phase-epitaxial growth of Inp/InGaAsP/InGaAs buried-structure avalanche photodiodes

An InP/InGaAsP/InGaAs avalanche photodiode with an effective guard-ring structure has been successfully fabricated. The diode has a planar structure with an n-InP layer buried by n?-InP in the multiplication region The structure has been grown on a (111)A-oriented InP substrate by two-step growth of liquid-phase epitaxy. Prior to the second growth of n?-InP a meltback technique was used to reduce dark current.     

Excess noise design of InP/GaInAsP/GaInAs avalanche photodiodes

An InP/GaInAsP/GaInAs avalanche photodiode (APD) with separate absorption and multiplication (SAM) regions has been designed taking into account the excess noise generated in GaInAsP and GaInAs. The multiplication factor dependence of the excess noise factorFhas been calculated using realistic electron and hole ionization rates in InP, GaInAsP, and GaInAs, assuming that the avalanche multiplication occurs not only in InP but in GaInAsP and GaInAs. The calculatedFvalues have been compared to the experimental ones measured on a planar-type InP/GaInAsP/GaInAs APD for illumination at a wavelength of 1.3 μm. It has been found the the calculated excess noise agrees very well with the experimental measurements. The limited ranges of device parameters in which the conditions of minimal excess noise, tunneling current, and charge pile-up are satisfied have been obtained. We conclude that the excess noise generated in GaInAsP and GaInAs should be considered in a practical device design.     

Excess noise in GaAs avalanche photodiodes with thin multiplicationregions

It is well known that the gain-bandwidth product of an avalanche photodiode can be increased by utilizing a thin multiplication region. Previously, measurements of the excess noise factor of InP-InGaAsP-InGaAs avalanche photodiodes with separate absorption and multiplication regions indicated that this approach could also be employed to reduce the multiplication noise. This paper presents a systematic study of the noise characteristics of GaAs homojunction avalanche photodiodes with different multiplication layer thicknesses. It is demonstrated that there is a definite “size effect” for multiplication regions less than approximately 0.5 μm. A good fit to the experimental data has been achieved using a discrete, nonlocalized model for the impact ionization process     

Time and frequency response of avalanche photodiodes with arbitrarystructure

A method is developed for solving the coupled transport equations that describe the electron and hole currents in a double-carrier multiplication (DCM) avalanche photodiode (APD) of arbitrary structure. This solution makes it possible to determine the time and frequency response of the device. The injection can be localized to one or both ends of the multiplication region, or distributed throughout an extended region where multiplication can occur concurrently. The results are applied to conventional APDs with position-dependent carrier ionization rates (e.g., a separate-absorption-grading-multiplication APD) as well as to superlattice multiquantum-well (MQW) structures where the ionizations are localized to bandgap transition regions. The analysis may also be used to determine the dark current and include the carrier trapping at the heterojunction interfaces. The results indicate that previous time-dependent theories only account for the tail of the time response under high-gain conditions and are inaccurate for high-speed devices     

High-speed flip-chip InP/InGaAs avalanche photodiodes with ultralowcapacitance and large gain-bandwidth products

Planar InP/InGaAs avalanche photodiodes (APDs) have been fabricated by adopting a flip-chart configuration and a monolithic lens structure. These APDs exhibit an ultralow capacitance of 70 fF, a quantum efficiency of 80%, a wide bandwidth of 7 GHz, and a large gain-bandwidth product of 80 GHz     

Characteristics in InGaAs/InP avalanche photodiodes with separated absorption and multiplication regions

Improved characteristics of compound semiconductor avalanche photodiodes with separated absorption and multiplication regions (SAM) are discussed. Temperature dependences of dark current and breakdown voltage show that the tunneling current in the narrow energy gap layer can be suppressed in InGaAs/InP APD's with the SAM structure. Dark currents above punch-through voltages, at which the depletion layer reaches the InP-InGaAs heterointerface, are caused by the generation-recombination process in the InGaAs and at the heterointerface. Dark currents near breakdown depend on the n-layer thickness and are strongly affected by the electric field strength in the ternary layer. Tunneling currents are dominant in diodes with thin n-InP layers, while the generation-recombination processes in the InGaAs layers are dominant in those with a thick n-InP layer. The dark current was as low as7.8 times 10^{4}A/cm²atM = 10when the interface electric field strength is reduced. A maximum multiplication factor of 60 was observed for the6 times 10^{-7}A initial photocurrent. Rise time and full width at half maximum in a pulse response waveform were 100 and 136 ps, respectively, atM = 10.