Magnetotransport in a two-subband AlGaN/GaN heterostructure in the presence of mixed disorder

¹ Université Montpellier 2 and CNRS, Laboratoire Charles Coulomb UMR 5221, 34095 Montpellier, France
² CRHEA-CNRS UPR 10, rue B. Grégory, Parc de Sophia Antipolis, 06560 Valbonne, France

^a e-mail: wilfried.desrat@univ-montp2.fr

Received: 19 February 2014
Revised: 10 September 2014
Accepted: 23 September 2014
Published online: 23 October 2014

Abstract

We present magnetotransport measurements on a high electron density AlGaN/GaN heterostructure with two subbands populated at T = 1.6 K. The transport scattering times, τ_tr, of each subband are first derived at low magnetic field by taking into account the magneto-intersubband scattering term. Then the quantum scattering times, τ_q, are extracted from independent Dingle plots, obtained at higher magnetic fields. All scattering times are studied as a function of the total electronic density, increased by the persistent photo-conductivity effect. A standard modelization, based on all common scattering mechanisms, reveals that the transport scattering time is governed by the short-range AlGaN/GaN interface roughness (IR) scattering, whereas the quantum scattering time is due to the smooth potential induced by remote ionized impurities (II) at the GaN surface. This intermediate situation of mixed disorder, where the τ_tr/τ_q ratio is greater than one, does not indicate that the mobility is limited by Coulomb scattering. It is due to the unusual condition, .