Calculation of vertical and horizontal mobilities in InAs/GaSb superlattices

Abstract

Superlattice (SL) devices such as infrared detectors and quantum-cascade lasers rely on efficient transport of carriers perpendicular to the SL layers by drift and/or diffusion. While horizontal mobilities are measured routinely, measurements of perpendicular-carrier mobilities require nonstandard experimental techniques such as the geometric magneto-resistance. Here we show how perpendicular mobilities can be estimated from horizontal mobility measurements and calculated mobilities. We treat low-temperature horizontal and vertical transport in SL on an equal footing by calculating both mobilities using the same interface roughness scattering (IRS) model from a rigorous solution of the Boltzmann transport equation. The calculation is specialized to the case of InAs/GaSb SLs, which are of current interest in the development of third-generation infrared detector focal plane arrays. The results are compared to available data.

A study of vertical and in-plane electron mobility due to interface roughness scattering at low temperature in InAs/GaSb type-II superlattices

“…Âju k 0 z ðÀaÞj 2 Âju k z ðÀaÞj 2 ) dðEðkÞÀEðk 0 ÞÞ: (14) This equation encapsulates the essential difference between the calculations of Szmulowicz et al 17 and the work presented in this paper. In particular, Szmulowicz et al have assumed that the periodic boundary conditions (and, hence, the wave-function moduli) at z ¼ 6a are equal, whereas in our model we have used ju kz ðaÞj 2 6 ¼ ju kz ðÀaÞj 2 , and we have substituted the exact value of the wave function at each interface.…”

Theoretical Aspects of Minority Carrier Extraction in Unipolar Barrier Infrared Detectors

“…For this superlattice, the vertical and horizontal effective masses are very similar, but there can be substantial differences between vertical and horizontal scattering times because of interface roughness. [41][42][43] We believe the different scattering times led to the observed electron mobility anisotropy, not the different vertical and horizontal electron effective masses. We should also remark that the conductivity effective masses reported here are computed for equilibrium carrier populations.…”

Performance analysis of an N-structure type-II superlattice photodetector for long wavelength infrared applications

“…µ h , τ h and µ e , τ e are assumed to be 300 cm 2 /Vs, 4 ns and 3000 cm 2 /Vs, 4 ns, respectively. These assumptions are based on the published literature [19][20][21][22][23] and [17,19,[24][25][26]]. …”