Temperature Dependence Of Diffusion Length Research Articles

Temperature dependence of diffusion length and mobility in mid-wavelength InAs/InAsSb superlattice infrared detectors

In the past decade, infrared detectors with InAs/InAsSb (Gallium-free) type-II strained layer superlattice absorbers became a technology of interest for many imaging applications. In this work, we study the dependence of minority carrier (hole) transport, absorption coefficient, and quantum efficiency (QE) of a 5.6 μm cutoff wavelength mid-wavelength infrared InAs/InAsSb detector on temperatures and applied bias. We found that the minority carrier lifetime is very long (τ ≈ 5.5 μs) and is temperature independent in the temperature range T = 50–150 K. The back-side illuminated QE without anti-reflection coating increases from ∼30% at T = 50 K to ∼60% at T = 180 K. The minority carrier (hole) diffusion length, Ldh, was found from QE and absorption coefficient. The hole diffusion length at T = 50 K is Ldh = 2.4 μm and increases monotonically to Ldh = 7.2 μm at T = 180 K. The hole mobility, calculated from diffusion length and minority carrier lifetime, is μh = 4.5 cm2/V s at T = 50 K and increases with temperature to reach μh = 7.2 cm2/V s at T = 150 K. In addition, we find that at lower temperatures where the diffusion length is shorter, the stronger QE dependence on applied bias is due to minority carrier collection from the depletion region, whose width increases with applied bias.

Temperature dependence of diffusion length, lifetime and minority electron mobility in GaInP

The mobility of electrons in double heterostructures of p-type Ga0.50In0.50P has been determined by measuring minority carrier diffusion length and lifetime. The minority electron mobility increases monotonically from 300 K to 5 K, limited primarily by optical phonon and alloy scattering. Comparison to majority electron mobility over the same temperature range in comparably doped samples shows a significant reduction in ionized impurity scattering at lower temperatures, due to differences in interaction of repulsive versus attractive carriers with ionized dopant sites. These results should be useful in modeling and optimization for multi-junction solar cells and other optoelectronic devices.

Excitonic transport in ZnO

Abstract

Photoluminescence of deep levels in (CdZn) Te-correlation with diffusion length measurement

Photoluminescence of deep levels near mid-gap in P-(Cd1−xZnx)Te (x≈0.05–0.07) grown by the vertical gradient freezing method was investigated. Correlation with recombination properties manifested by temperature dependence of diffusion length of minority electrons and the corresponding mobility-lifetime product was studied. Low-temperature photoluminescence (PL) in the spectral range 0.68–1.3 eV and a temperature dependence of diffusion length of minority electrons (DL) measured by EBIC in the temperature range 60–300 K on both as-grown and annealed samples (800°C and 900°C) were investigated. We observed, that while as-grown samples exhibited a steep increase in DL with decreasing temperature in the temperature range 60–140 K, annealing and subsequent quenching resulted in a significant decrease of DL at these temperatures. Photoluminescence band with a peak at approx. 0.84 eV in annealed samples with increased recombination and therefore low DL was observed, while no such peak was detected in the as-grown samples with high DL. Luminescence in the ≈0.8 eV band is usually attributed to a VCd related defect which is supposed to act as a recombination centre. It can be concluded, that a correlation between effects of increased recombination manifested by decreased values of DL at temperatures 60–140 K and detection of the ≈0.8 eV PL band was observed. Reduction of the mobility-lifetime product by increased recombination in (CdZn)Te single crystals is therefore probably connected with a presence of a VCd-related defect.