Influence of electron mobility modeling on DC I-V characteristics of WZ-GaN MESFET

We report on the drift-diffusion based simulation of wurtzite (WZ) GaN MESF ET. The main emphasis is put on the influence of electron mobility modeling on de current-voltage (I-V) characteristics of the WZ-GaN MESFET. Two diff erent analytical expressions are used for the electron mobility as a functi on of electric held, The first model is based on a simple saturation of the steady-state drift velocity with electric field (conventional three-parame ter model). The other model is more realistic since it well reproduces the drift velocity-held characteristics obtained by Monte Carlo (MC) calculatio ns, revealing the peak drift velocity with subsequent saturation at higher electric fields. Thus, it should be implemented in the drift-diffusion mode l for a following device simulation. However, the MC electron transport dat a for WZ-GaN are influenced by the specific choice of the material and band structure parameters, resulting in a variation of drift velocity-field cha racteristics [1], In addition, it should be noted that the MC simulation al so neglects crystal defects in GaN, which, for example, might lead to uncon trolled electron compensation and additional electron scattering. In the present study we show that the de I-V characteristics of the WZ-GaN MESFET are strongly affected by the MC-like electron mobility model, in par ticular by the peak steady-state velocity and the shape of the velocity-hel d characteristics even for the same drift velocity saturation level.