Considerations for DD Simulation at Cryogenic Temperature

We discuss device models employed in the drift-diffusion simulation of MOSFET transistors at deep cryogenic temperatures. We report potential issues of the commonly used models (the Philips unified mobility model, the high field saturation model, the incomplete ionization model, and the quantization model) at low temperatures and how to resolve the issues. In addition, we present a band tail model to capture the subthreshold slope saturation at low temperatures. We also discuss how to obtain the initial solution and perform the bias ramping to avoid convergence issues. As an application, we study the temperature-dependent operation of a gate-all-around transistor down to 4 K.

I. Introduction

MOSFET Operations at deep cryogenic temperatures have recently gained attention with the advancement of quantum computers [1]. While there exist studies on the drift-diffusion (DD) model at around 77 K [2], [3], DD simulation down to the liquid He temperature (≃ 4 K) important for quantum applications has not been extensively studied [4] –[7].