Mechanism of hot electron electroluminescence in GaN-based transistors

Abstract

The nature of hot electron electroluminescence (EL) in AlGaN/GaN high electron mobility 
\ntransistors is studied and attributed to Bremsstrahlung. The spectral distribution has been 
\ncorrected, for the first time, for interference effects due to the multilayered device structure, 
\nand this was shown to be crucial for the correct interpretation of the data, avoiding artefacts 
\nin the spectrum and misinterpretation of the results. An analytical expression for the spectral 
\ndistribution of emitted light is derived assuming Bremsstrahlung as the only origin and 
\ncompared to the simplified exponential model for the high energy tail commonly used for 
\nelectron temperature extraction: the electron temperature obtained results about 20% lower 
\ncompared to the approximated exponential model. Comparison of EL intensity for devices 
\nfrom different wafers illustrated the dependence of EL intensity on the material quality. The 
\npolarization of electroluminescence also confirms Bremsstrahlung as the dominant origin of 
\nthe light emitted, ruling out other possible main mechanisms.