The set of classical drift-diffusion device equations has been applied to fully distributed traveling-wave heterojunction phototransistor structures (TW-HPTs). The two-dimensional physical modeling includes an equivalent circuit transmission-line solver in common with previous approaches to analyze traveling-wave devices. The addition of a full physical model has shown for the first time the potential RC limitations that still exist for transistor structures in the traveling-wave regime. While efforts can be made to reduce these limitations, they all have their drawbacks. As such we propose that the use of HPT gain is better suited to periodically distributed traveling-wave devices.
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