GaN-based heterojunction transistors are being developed with intensive efforts for high-efficiency power converters, owing to their capabilities of delivering lower conduction/switching losses, higher switching frequency, and higher operating temperatures compared to conventional Si power devices. However, the development of GaN-based high-voltage power devices is still challenged by deep electron traps that are inevitable in state-of-the-art GaN-on-Si epitaxial heterostructures, which would increase the dynamic ON-resistance (R_ON) and resulting in additional power losses during high-voltage and high-frequency switching operations.

In this work, we proposed and developed a new way of suppressing adverse effects of electron traps and thus enhancing the GaN power devices’ dynamic...[ Read more ]

GaN-based heterojunction transistors are being developed with intensive efforts for high-efficiency power converters, owing to their capabilities of delivering lower conduction/switching losses, higher switching frequency, and higher operating temperatures compared to conventional Si power devices. However, the development of GaN-based high-voltage power devices is still challenged by deep electron traps that are inevitable in state-of-the-art GaN-on-Si epitaxial heterostructures, which would increase the dynamic ON-resistance (R_ON) and resulting in additional power losses during high-voltage and high-frequency switching operations.

In this work, we proposed and developed a new way of suppressing adverse effects of electron traps and thus enhancing the GaN power devices’ dynamic performance by on-chip photon pumping. To realize this objective, the work was devoted to three parts:

First, a Schottky-on-heterojunction light-emitting diode (SoH-LED) was demonstrated on a p-doping-free AlGaN/GaN heterostructure, from which electroluminescence (EL) could be generated. The EL spectra included a yellow band, a blue band and a narrow GaN-bandedge UV emission at 3.4 eV. A model based on hot-electron induced surface states impact ionization was proposed to explain the underlying mechanisms of the hole generation and injection processes. With no additional epi-layers during the wafer growth and minimum process modification during device fabrication, the SoH-LED provides a unique on-chip photon source fully compatible with the GaN-on-Si power devices.

Second, a SoH-LED was seamlessly integrated onto the AlGaN/GaN high-electron-mobility transistor (HEMT) platform as an on-chip photon source. The surface and buffer trapping were intentionally induced to the HEMT and the following de-trapping processes were monitored w/ and w/o the light illumination of the on-chip integrated SoH-LED. Experimental results revealed that the photons from SoH-LED could effectively accelerate the electron de-trapping processes from both the surface and buffer traps, demonstrating the feasibility of using on-chip photon pumping to improve the dynamic performances of power HEMTs.

Finally, a compact photonic-ohmic-drain field-effect transistor, i.e. PODFET, was designed and demonstrated on a conventional GaN-on-Si power HEMT platform. The PODFET exhibited a simple yet effective approach to driving the compact photon source (i.e. SoH-LED) with the intrinsic channel current. During each switching event, the photon generation was switched ON in synchronization with the channel current, pumping electrons from the deep traps with ease and effectively suppressing dynamic R_ON degradation which was reduced from 50% in conventional device to 6% in PODFET under 600-V high-voltage switching. Without over-designed buffer structures, the PODFET provides a simple solution to sufficiently suppress the adverse effects of deep electron traps, resulting in lower overall cost and higher switching efficiency.