Growth optimization for low residual carriers in undoped midinfrared InAs/GaSb superlattices.

Reducing residual background carriers in InAs/GaSb superlattices (SLs) is an essential task to increase the operating temperature of photoconductive devices. This paper discusses how low-temperature Hall measurements were used to tune several SL growth parameters for the minimum residual carriers in a typical midinfrared 21 Å InAs/24 Å GaSb SLs designed for the 4 μm cutoff wavelength. Among the three growth parameters studied, neither growth temperature nor in situ postannealing significantly affected the intrinsic carrier type and doping concentration. The lowest carrier density of 1.8×1011 cm-2 was achieved at 400 °C. All SLs grown at 400 °C maintained the lowest density around 1.6×1011 cm-2 with or without postannealing. However, in-plane carrier mobility showed a slight improvement with annealing, especially at temperatures above 450 °C. The growth parameter most sensitive to the carrier density was interface control. With a minor variation in interface shutter sequence, the carrier density dramatically increased from ∼2×1011 to 5×1012 cm-2, and the corresponding mobility dropped from 6600 to 26 cm2/V s, indicating dramatic degradation of interfacial quality. All SLs investigated in this study were residually p-type. [ABSTRACT FROM AUTHOR]