Ballistic Transport in InP-Based HEMTs

Ballistic transport has been of interest in semiconductor devices for quite some time, and its effect has been used to predict quite-different device performance. Here, we investigate the role of ballistic transport in a short-channel InGaAs/InAlAs HEMT through full-band cellular Monte Carlo simulations. We can examine the contrast in behavior between when scattering mechanisms are present and when they are turned off. When the scattering processes are completely removed, the output characteristics show a distinct change in behavior over all drain voltages. This result is in qualitative agreement with prior arguments, suggesting that triodelike behavior should be expected due to enhanced drain-induced barrier lowering. However, we find that explicit band-structure effects are observable in the output characteristics of the ballistic transistor. We also find that this distinctive behavior gradually disappears as scattering is turned on, particularly in the drain end of the device. We also develop a method of determining the probability that electrons pass through the gate region in a ballistic manner in the presence of realistic scattering. Even when the gate is only 10 nm long, we find that this probability is only on the order of 50% in these devices. We also examine the ballistic ratio in our device as a function of gate length.