Different type-II InGaAs/GaAsSb quantum well design structures on InP substrate for mid-infrared
emission has been modeled by six band k•p method. The dispersion relations, optical matrix element,
optical gain and spontaneous emission rate are calculated. The effects of the parameters of quantum wells
(thickness, composition) and properties of cladding layers were investigated. For injected carrier
concentration of 5×1012 cm-2, peak gain values around 2.6-2.7 μm wavelengths of the order of 1000 cm-1
can be achieved, which shows that type-II InGaAs/GaAsSb quantum wells are suitable for infrared laser
operation beyond 2μm at room temperature.
This paper describes single photon detection for Ge on Si separate-absorption-charge-multiplication (SACM) avalanche
photodiodes and advances in quenching for InP/InGaAs single photon avalanche diodes.
This paper reports the results of modeling of the electrical characteristics of SWIR/MWIR p-i-n
photodiodes with type II InGaAs/GaAsSb multiple quantum wells (MQWs) as the absorption region. Bulk
based model with the effective band gap of the type-II quantum well structure has been used in modeling of
the experimental data. We investigated the dark current contributing mechanisms that are limiting the
electrical performance of the diode. The quantitative simulation of the I-V characteristics shows, that the
200K to 290K performance of InGaAs/GaAsSb photodiodes is dominated by generation-recombination
processes at the small reverse bias (-5V~0V). Above -10V, the trap-assisted tunneling current and direct
tunneling current begin to dominate.
GaInAs/GaAsSb type-II multiple quantum wells (MQWs) grown on InP substrates by molecular beam epitaxy (MBE)
were investigated for potential use in p-i-n photodiodes operating in the mid-infrared spectral region. In these quantum
well structures, electrons and holes are spatially separated. The resulting spatially indirect type-II detection occurs at
longer wavelength than the spatially direct intraband recombination in either GaInAs or GaAsSb. A 4-band k · p
Hamiltonian model was employed to calculate the detection wavelengths and wavefunction overlaps. A p-i-n structure
with 100 pairs of Ga0.66In034As (~7.0 nm)/GaAs0.25Sb0.75 (~5.0 nm) MQWs structure with operation wavelength of above
3.0 μm was designed and grown by MBE. The compressively strained GaAsSb layers are strain-compensated by tensile
strained GaInAs. Photo response of above 3 μm was observed by room temperature responsivity measurements.
Avalanche Photodiodes (APDs) are key components in modern lightwave communications systems. When compared to p-i-n diodes, APDs provide internal gain via impact ionization which leads to higher sensitivity. In addition, with proper device design, high gain bandwidth products can also be achieved. In this paper, we describe our work in making high speed, low noise APDs - operating at 1300 - using GaAs based multiplication regions. Our results to date have lead to a resonant cavity enhanced (RCE) APD, operating at 1310 nm, with an external quantum efficiency of 36% and an effective k factor of 0.1.
This paper surveys recent work in several photodetector areas including high-speed, low-noise avalanche photodiodes, high-power photodiodes, solar-blind ultra-violet PIN photodiodes, and quantum dot infrared photodetectors (QDIPs).
This paper surveys recent work in several photodetector areas including high-speed, low-noise avalanche photodiodes, solar-blind ultra-violet PIN photodiodes, and quantum dot infrared photodetectors (QDIPs).
InP/In0.53Ga0.47As avalanche photodiodes (APDs) have been widely deployed in high-bit-rate, long-haul fiber optic communication systems due to the higher sensitivity, relative to a PIN photodiode, afforded by internal gain of the APD. Owing to their materials and structural limitations it is uncertain whether the performance of InP-based APDs will be adequate for 10 GB/s systems and subsequent higher- speed systems. One of the impediments for the InP-based APDs is the fact that InP has roughly equal electron and hole ionization rates. This result in a symmetric multiplication process with relatively high multiplication noise and the gain-bandwidth product of an APD are primarily determined by the structure of the multiplication region. Recently, it has been reported that submicron scaling of the multiplication region thickness leads to lower multiplication noise and higher gain-bandwidth products. This is due to the nonlocal nature of impact ionization, which can be neglected if the thickness of the multiplication region is much greater than the 'dead length', the distance over which carriers gain sufficient energy to impact ionize. The advantage of thin multiplication regions, i.e., those for which, the dead space accounts for a significant portion of the total thickness, is that the number of ionization chains that result in multiplication greatly in excess of the average gain is reduced, which in turn yields lower noise for a given gain. In this paper we describe materials and structural modifications to the thin multiplication regions that result in even lower excess noise. For gains <EQ 20 APDs with thin AlxGa1-xAs multiplication layers have achieved excess noise factors less than twice the shot noise. We have also shown that ultra low noise can be achieved with an Impact-Ionization-Engineered approach that utilizes heterojunctions to incorporate adjacent regions with low and high ionization rates.
A large number of novel devices have been recently demonstrated using wafer fusion to integrate materials with different lattice constants. In many cases, devices created using this technique have shown dramatic improvements over those which maintain a single lattice constant. We present device results and characterizations of the fused interface between several groups of materials.
Recent progress on the use of liquid organometallic sources for replacing the group V compressed gases looks particularly encouraging. We have grown both strained and unstrained InxGa1-xAsyP1-y/InP and In0.53Ga0.47As/InP quantum well materials and devices in a non-hydride metalorganic chemical vapor deposition (MOCVD) system using liquid group V sources, tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP). Very low threshold current strained InGaAsP/InP quantum well laser diodes have been grown using TBA and TBP for the first time. Single 90 angstrom InGaAsP quantum well lasers emitting at 1.55 micrometers displayed threshold current densities of 121 A/cm2 for a 1.6% compressively strained SQW, and 249 A/cm2 for an unstrained SQW at a cavity length of 3500 micrometers . Unstrained ternary (In0.53Ga0.47As) single quantum well laser diodes exhibited extremely low threshold current densities (Jth equals 220 A/cm2 for broad area devices 3.5 mm in cavity length). These values indicate that TBA and TBP are viable replacements for the more hazardous compressed gases, arsine and phosphine.
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