Date of Award

2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Iyer, Dr. Shanthi

Abstract

The distinguishing features of dilute nitride III-V semiconductors lie in the large simultaneous reduction in the band gap and lattice parameter when N is incorporated in small amounts in an otherwise wide band gap III-V material. In particular, N incorporation in InSb is attracting great attention due to its potential applications in the long wavelength infrared (LWIR) applications. However, the relatively small atomic size of N with respect to Sb makes the growth of good quality InSbN layers challenging with effective N incorporation. In this dissertation we present a correlation of the molecular beam epitaxial growth parameters on the type of N bonding in the InSbN epilayers. Lower growth temperatures of ~290 °C were observed to favor formation of more substitutional N (In−N) and less interstitial N (Sb−N, N−N and In−N−Sb) in the InSbN epilayers. The types of N-bonding were observed to have dominant effect on the structural, vibrational, electrical and optical properties of these dilute nitride epilayers grown on GaAs substrates. As-grown epilayers with high N incorporation of 2.6 % were observed to exhibit a blue shift in the absorption edge to 0.132 eV due to Moss-Burstein effect. Both ex-situ and in-situ annealing at 430 °C improved the quality of the layers as attested to by the micro Raman spectra, reduced the carrier concentration to ~1016 cm-3, increased the mobility (µ) to ~13,000 cm2/V-s and red shift the absorption edge to ~10 µm at room temperature (RT). Amongst the heterostructures examined, consisting of different combination of thickness of InSb and InSbN layers, the growth of a relatively thick (~1.4 µm) InSb buffer layer was found to prevent the propagation of rotational and threading dislocations into the subsequent InSbN epilayers. Thus, high RT µ exceeding 40,000 cm2/Vs and an optical absorption edge at ~12 µm in the LWIR range have been achieved for 450 °C ex-situ annealed 0.4 µm InSbN/ 1.4 µm InSb/ GaAs heterostructure.

Share

COinS