Two materials studies on residual background carriers and density dependent carrier mobilities in InAs/GaSb superlattices

Frank Szmulowicz 1Said Elhamri 2Heather J. Haugan 3Bruno Ullrich 4Gail J. Brown 5William C. Mitchel 5

1. University of Dayton Research Institute (UDRI), 300 College Park Ave., Dayton, OH 45469, United States
2. University of Dayton, Physics Department (UD), 300 College Park Ave, Dayton, OH 45469, United States
3. Universal Technologies Corporation (UTC), 1270 North Fairfield Road, Dayton, OH 45432, United States
4. Bowling Green State University (BGSU), Bowling Green, Ohio 43403, United States
5. Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, OH 45433, United States


Material properties of InAs/GaSb type-II superlattices (SLs) are sensitive indicators of SL growth quality and of the eventual performance of devices made from these materials. In InAs/GaSb SLs, electrons move predominantly in the InAs layer, where they are affected by intrinsic and extrinsic scattering mechanisms, including interface roughness scattering (IRS).. The mid-infrared 7 ML InAs/8 ML GaSb superlattices (SLs) were grown by molecular beam epitaxy at growth temperatures between 370 and 430 C in order to study the intrinsic characteristic of background carriers.  Grown SLs were all residual p-type with carrier densities in the low 1011 cm-2, and a minimum density of 1.8x1011 cm-2 was obtained from the SL grown at 400 C.  With increasing growth temperature, the in-plane carrier mobility decreased from 8740 to 1400 cm2/Vs due to increased interfacial roughness, while the
photoluminescence intensity increased six fold due to a decrease in the nonradiative defect densities. Next, we report on a study of the in-plane carrier mobility in InAs/GaSb superlattices as a function of carrier density. Instead of using a number of differently doped samples, we use the persistent photoconductivity-effect to vary the carrier density over a wide range from n- to p-type in single samples and perform Hall effect measurements. Hence, our data are not obscured by sample to sample non-uniformities. We demonstrate that low-temperature in-plane mobilities are limited by screened interface roughness scattering (IRS), although present models of two-dimensional carrier screening of IRS lead to limited agreement with our data.


Presentation: Oral at E-MRS Fall Meeting 2009, Symposium D, by Frank Szmulowicz
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-06-21 23:43
Revised:   2009-08-25 11:16