Publications

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

Casias, Lilian K.; Morath, Christian P.; Steenbergen, Elizabeth H.; Webster, Preston T.; Kim, Jin K.; Cowan, Vincent M.; Balakrishnan, Ganesh; Krishna, Sanjay

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 minority carrier electrons. However, there are added challenges to determining the hole carrier concentration in narrow bandgap InAsSb 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) are 1.6 × 1018 cm−3 (2.3 × 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 × 1018 cm−3. A surface treatment experiment is conducted to associate one of the electron conducting populations to the surface. Variable temperature (15–390 K) measurements confirmed the different carrier species present in the sample and enabled the extraction of the bulk heavy hole, interface carriers and surface electron transport properties. For the bulk carrier, a thermal activation of intrinsic carriers is identified at high temperatures with a bandgap of EG ∼ 258 meV and the low temperature data suggests an activation energy of EA ∼ 22 meV for the Be dopant atoms. Finally, temperature analysis confirms a surface carrier electron with resulting mobilities and sheet concentrations at 30 K (300 K) of 4500 cm2 V−1 s−1 (4300 ± 100 cm2 V−1 s−1) and 5.6 × 1010 cm−2 (6 × 1010 ± 2 × 1010 cm−2), respectively.