A Normally-off GaN MISFET with High Vth uniformity

ganfetex06.in : A Normally-off GaN MISFET with High Vth uniformity

Requires: Blaze
Minimum Versions: Atlas 5.28.1.R

This example demonstrates the simulation of a GaN metal-insulator-semiconductor field effect transistor (MISFET) with Piezo Neutralization Technique (PNT).

This example is based on the work of:

Ota, K. et. al. "A Normally-off GaN FET with High Threshold Voltage Uniformity Using A Novel Piezo Neutralization Technique", IEDM 2009, pp. 153-156.

The features of the PNT structure are described below and simulated with Blaze

The first feature is an AlGaN buffer layer to realize a normally-off operation. The polarization charges at the interface between the AlGaN buffer and the GaN channel act as virtual p-type doping and contribute to simustaneously increase Vt and charge density in the channel.The band diagram and IdVg simulations demonstrate the impact of the buffer Al-concentration on the electron-channel energy beneath the gate and Vth respectively

The second is an Al0.07Ga0.93N PNT layer having an identical Al composition with the buffer layer to realize high Vth uniformity. Since PNT and buffer layers have an identical Al mole fraction, the polarization charges formed between these layers are completely canceled and hence, a flat band condition occurs throughout the PNT layer. Vth dependence on the AlGaN layer thickness under the gate electrode was simulated. For the GaN FETs with the PNT structure, the Vth is not affected by the variation of AlGaN thickness whereas it varies for the conventional Al0.15Ga0.85N/GaN single heterojunction FETs.

The last is the 2nd supply layer at the region outside the gate electrode to reduce on-resistance of the GaN FET. Since the 2nd supply layer is consisted of AlGaN with higher Al composition than that for the 1st supply layer, a large amount of 2DEG is produced both in the channel layer and the PNT layer when enabling the POLARIZATION model of the MODELS statement. This polarization model accounts for the fact that a layer may not have homogenous strain due to e.g. recessed gates so polarization charge is calculated locally.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.