On the correlation between drain and gate currents and light emission in GaAs – PHEMTs biased in the impact ionization regime

In this work we investigate, by means of electrical and both spectral and integral electroluminescence measurements, the light emission mechanisms in AlGaAs/InGaAs/GaAs pseudomorphic HEMTs biased at high drain voltage. Under these conditions impact ionization and light emission take place due to hot electrons. We examine the distinctive features of the light spectra (in particular, using a high-resolution monochromator the spectrum peak is shown to possess a fine structure due to quantized levels of the InGaAs channel), their respective temperature and bias dependence, and by means of physical considerations and a study of the correlation between the light intensity and the device currents we speculate on the physical mechanisms giving rise to photon emission in the different energy ranges.