Electroluminescence measurement of InAlAs/InGaAs HEMTs lattice-matched to InP substrates

InAlAs/InGaAs HEMTs latticed-matched to InP substrates are promising devices for high-speed application owing to their excellent high-frequency performances. Their low breakdown voltage and the appearance of a kink, however, limit their application to practical circuits. The impact ionization at the drain edge in the channel has been pointed out as the origin of these phenomena. Several authors have used electroluminescence (EL) from FETs composed of compound semiconductors to investigate the impact ionization in their channels. For InGaAs-based FETs, EL with energy far higher than the band gap of the channel has been already investigated. In this paper, we report measurements of the EL appearing from the top of the InAlAs/InGaAs HEMTs for energy lower than 1 eV at room temperature. We mainly discuss the carrier temperature extracted from the spectrum and the spatial distribution of the intensity. We also report the EL appearing from the cleaved side of the FET channel.