Analysis of hot carrier transport in AlGaAs/InGaAs pseudomorphic HEMT's bymeans of electroluminescence

The carrier transport phenomena occurring in pseudomorphic AlGaAs/InGaAs HE MT's biased in the on-state impact-ionization regime is analyzed in this pa per. We confirm the presence, in the electroluminescence spectra of pseudom orphic HEMT's, of a dominant contribution due to electron-hole recombinatio n, and we identify a composite peak due to recombination of cold carriers. We analyze the recombination peak using a high-resolution monochromator, wh ich reveals the fine structure due to transitions between electron and hole subbands in the channel quantum well, thus providing useful data concernin g the properties of the InGaAs HEMT channel. We also demonstrate that recom bination between nonenergetic electrons and holes occurs in the gate-source region, as already observed in InAlAs/InGaAs HEMT's on InP, This recombina tion emission is superimposed to a less intense contribution mostly coming from the gate-drain region. This contribution has a nearly Maxwellian distr ibution which extends to fairly high energies (>3 eV) and has equivalent te mperatures in the 1000-3000 K range, Finally we show evidence of recombinat ion in the AlGaAs layers (observed at high electric field), which demonstra tes, in these devices, real space transfer of both electrons and holes,