ANALYSIS OF DELTA-DOPED AND UNIFORMLY DOPED ALGAAS/GAAS HEMTS BY ENSEMBLE MONTE-CARLO SIMULATIONS

Transport properties and device performance of delta-doped and uniformly doped AlGaAs/GaAs high electron mobility transistors (HEMT's) with identical threshold voltages and gate capacitors are investigated with two-dimensional, self-consistent ensemble Monte Carlo simulations. The model includes the effects of real-space transfer and carrier degeneracy, as well as the influence of DX centers and surface states. A one-to-one comparison of simulation results for the two devices demonstrates superior performance for the delta-doped HEMT and provides physical basis for the observed improvements. In particular, the delta-doped HEMT maintains its superior device performance as gate bias is increased. The simulations provide reasons for these improvements. The predicted advantages of the delta-doped HEMT include high channel electron density and high channel drift velocity, which stem primarily from improved channel electron confinement, reduced parallel conduction at high gate-to-source voltage, and reduced peak channel electric field. The advantages of delta-doped HEMT are manifested in higher transconductance and improved drain current drive capability at a wider gate-to-source voltage, which are desirable properties for ultra-fast digital and microwave device applications.