Abstract
In this work, we propose a simple and yet accurate physical model to describe the figures-of-merit (FOMs) of lateral GaN power devices. While the performance limit of vertical devices is well understood, the FOMs of lateral devices are not properly described by current models. This work investigates the specific characteristics of the depletion in lateral devices, particularly focusing on the substantial potential of Polarization Super Junctions (PSJs) compared to conventional High-Electron-Mobility Transistors (HEMTs). Our results show that PSJs can result in more than a 10-fold decrease in specific on-resistance for the same breakdown voltage compared to HEMTs, which can be further improved by the use of multi-channel heterostructures. In addition, we demonstrate that PSJs lead to a significant reduction of the $R_{ON}\times E_{\mathrm{ oss}}$ figure-of-merit, both in the case of negligible and dominating parasitic contributions. This model enables a proper evaluation of the main figures-of-merit of lateral GaN power devices and shows the potential of PSJs to reduce both the DC and switching losses in power devices.
Highlights
GaN-on-Si lateral devices have shown outstanding potential for power conversion applications and a substantial improvement in their performance has been achieved in recent years [1], [2]
We compare the RON,sp vs VBR performance of polarization super junctions (PSJs) and HighElectron-Mobility Transistors (HEMTs) and show that a more than 10-time decrease in RON,sp for the same VBR can be achieved by PSJs with sheet resistance (Rsh) of 300 Ω/sq, which can be further improved by the use of multi-channel heterostructures to reduce Rsh down to ~ 80 Ω/sq [17]–[22]
We compare the switching losses of PSJs and HEMTs showing that a significant improvement in the RON x Eoss figureof-merit, where Eoss is the energy stored in the device output capacitance, is achieved by PSJ devices both in the case of negligible and dominating parasitic contributions. This model enables a proper evaluation of the main figures-of-merit of lateral GaN power devices and shows the potential of PSJs to reduce both the DC and switching losses in power devices
Summary
GaN-on-Si lateral devices have shown outstanding potential for power conversion applications and a substantial improvement in their performance has been achieved in recent years [1], [2]. The performance of current GaN HighElectron-Mobility Transistors (HEMTs) is still far below what is thought to be the limit for such devices [3] Their lateral architecture combined with the large density of the twodimensional electron gas (2DEG) results in a peaked off-state electric field at the gate edge, which severely reduces the maximum achievable breakdown voltage (VBR). To address this limitation, polarization super junctions (PSJs) have been proposed [4]–[9], which take advantage of the polarization fields naturally formed in GaN heterostructures to achieve charge balance. This model enables a proper evaluation of the main figures-of-merit of lateral GaN power devices and shows the potential of PSJs to reduce both the DC and switching losses in power devices
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