Temperature mapping of Al_0.85In_0.15N/AlN/GaN high electron mobility transistors through micro-photoluminescence studies

École Polytechnique Fédérale de Lausanne (EPFL), Institute of Quantum Electronics and Photonics, 1015 Lausanne, Switzerland

Corresponding author: marcus.gonschorek@epfl.ch

Received: 17 February 2009
Accepted: 18 March 2009
Published online: 20 May 2009

Abstract

Crack-free lattice-matched Al_0.85In_0.15N/GaN heterostructures were grown on sapphire substrates with barrier thicknesses up to 100 nm which exhibit very high polarization-induced electron sheet density ( cm⁻²) located at the heterointerface. These layers have been further processed as high electron mobility transistors (HEMTs). Optical characterization of these structures was carried out by photoluminescence and microphotoluminescence (PL) for different biased voltages. The insertion of an InGaN back-barrier unambiguously reveals that spatially direct optical recombinations occur within the AlInN alloy. Since the GaN excitonic bandgap is very sensitive to local temperature changes, the PL technique allows mapping very precisely the actual local temperature distribution in biased HEMT devices. For a gate length of 1.5 m temperatures up to 1130 K were found at a drain-source voltage of 20 V thus indicating the presence of a hot phonon bath.