2016年7月27日星期三

A theoretical discussion on the internal quantum efficiencies of the epitaxial single crystal GaSb thin film cells with different p–n junctions

Highlights

The internal quantum efficiency (IQE) of epitaxial GaSb thin film cell was predicted.
The optimal thickness of the base region was obtained for the maximal IQE.
The optimal range of the bottom surface recombination velocity was obtained.
Increasing the hole Shockley–Read–Hall lifetime will greatly increase the IQE.

Abstract

As promising candidates for thermophotovoltaic energy conversion systems, epitaxial thin film III–V cells have gained increasing attention due to their potential for reduced weight. However, few studies have been done to date to enhance the performance of epitaxial single crystal GaSb thin film cells. In this work, the internal quantum efficiencies of epitaxial single crystal GaSb thin film cells with Zn-diffused and epitaxial p–n junctions were predicted with models verified using the corresponding experimental results. The results are the first to indicate that, for the former, when the base region thickness is approximately equal to minority carrier diffusion length, the maximal IQE can be obtained and it is notably higher than the IQE of GaSb bulk cell at wavelengths from 800 to 1700 nm. Reducing bottom surface recombination velocity and increasing hole Shockley–Read–Hall lifetime could also increase the IQE. While for the latter, the results demonstrated that the optimal base region thickness is also approximately equal to minority diffusion length, and reducing emitter region thickness will increase the IQE when the base region is optimized. The comparison of the two optimized GaSb thin film cells showed that the GaSb thin film cell with epitaxial p–n junction has a higher IQE.

Keywords

  • Epitaxial single crystal GaSb thin film cell
  • Zn-diffused p–n junction
  • Epitaxial p–n junction;
  • Internal quantum efficiency

2016年7月26日星期二

Mid-wave T2SLs InAs/GaSb single pixel PIN detector with GaAs immersion lens for HOT condition

Highlights

We presented the mid-wave single (λ50% cut-off = 5.2 μm) pixel mesa PIN T2SLs InAs/GaSb detector with ∼1.1 mm GaAs substrate converted into immersion lens to increase detectivity by ∼10.
At = 230 K reached by thermoelectrical cooling, presented detector exhibits detectivity, D* ∼ 2 × 1010 cm Hz1/2/W, under reverse bias 200 mV.
At = 300 K presented detector exhibits detectivity, D ∼ 4 × 109 cm Hz1/2/W at 300 K, under 500 mV.
Presented results are higher than PIN architectures with the same and lower cut-off wavelength grown on GaAs without immersion lens and grown on GaSb substrates.
Detectivity for MWIR (λ50% cut-off = 5.1 μm) multi-layer MCT Auger suppressed, unbiased heterostructure with comparable λ50% cut-off = 5.2 μm, GaAs immersion lens is one order of magnitude higher than PIN T2SLs InAs/GaSb due to SRH defects.

Abstract

In this paper we report on high operating temperature mid-wave infrared detector based on type-II superlattice InAs/GaSb mesa PIN architecture with 50% cut-off wavelength ∼5.2 μm at 230 K. The 1.1 mm thick GaAs substrate was converted into immersion lens to limit an influence of the defects occurring during growth on GaAs substrate and to increase detectivity, ∼2 × 1010 cm Hz1/2/W at 230 K, under reverse bias 100 mV and ∼4 × 109 cm Hz1/2/W at 300 K, under 500 mV. Presented results are better than PIN architectures with the same and lower cut-off wavelength grown on GaAs without immersion lens and grown on GaSb substrates.

Keywords

  • T2SLs InAs/GaSb
  • PIN IR detectors
  • GaAs immersion lens