Carrier concentration and transport in Be-doped InAsSb for infrared sensing applications

Accurate p-type doping of the active region in III-V infrared detectors is essential for optimizing the detector design and overall performance. While most III-V detector absorbers are n-type (e.g., nBn), the minority carrier devices with p-type absorbers would be expected to have relatively higher quantum efficiencies due to the higher mobility of their constituent minority carrier electrons. However, correctly determining the hole carrier concentration in narrow bandgap InAsSb may be challenging due to the potential for electron accumulation at the surface of the material and at its interface with the layer grown directly below it. Electron accumulation layers form high conductance electron channels that can dominate both resistivity and Hall-effect transport measurements. Therefore, to correctly determine the bulk hole concentration and mobility, temperature- and magnetic-field-dependent transport measurements in conjunction with Multi-Carrier Fit analysis were utilized on a series of p-doped InAs0.91Sb0.09 samples on GaSb substrates. The resulting hole concentrations and mobilities at 77 K (300 K) were 1.6 x 1018 cm-3 (2.3 x 1018 cm-3) and 125 cm2 V-1 s-1 (60 cm2 V-1 s-1), respectively, compared with the intended Be-doping of ~2 x 1018 cm-3.