Search

In this letter, we investigate the threshold voltage ( ${V}_{\text {TH}}$ ) shift in a p-GaN gate AlGaN/GaN transistor by designed gate-bias pulse measurements. It was found that the forward gate bias causes positive ${V}_{\text {TH}}$ shift. The dynamics of electron trapping was revealed from the dependences of the consequent ${V}_{\text {TH}}$ shift on the bias duration at different voltages. A time constant smaller than 0.1 ms for the ${V}_{\text {TH}}$ shift saturation at 6-V gate bias was obtained. It was also found that the ${V}_{\text {TH}}$ became inversely proportional to the gate-bias voltages exceeding 7 V. This inverse proportionality of the ${V}_{\text {TH}}$ shift resulted from the threshold of the hole-injection/electroluminescence (EL) and the sequential optical pumping effect on the electron traps. The EL emission was confirmed by a self- and in-situ photon detection measurement.

Integration of a photon source into the AlGaN/GaN high election mobility transistor (HEMT) platform will realize the functionality of on-chip optical pumping of deep electron traps which suppress the dynamic performances of power HEMTs. Here, we report a Schottky-on-heterojunction light-emitting diode (SoH-LED) realized on the p-doping-free lateral AlGaN/GaN heterostructure. A physical mode based on hot electron induced surface states impact ionization was proposed to explain the hole generation and injection processes in this p-doping-free SoH-LED. Since the SoH-LED shares identical epitaxial structures with HEMT, integration of SoH-LED and HEMT requires no additional epi-layers during the wafer growth and minimum process modification during device fabrication. The SoH-LED structure was seamlessly integrated into the HEMT platform as an on-chip photon source. Experiment results showed that the SoH-LED photons can effectively assist the electron de-trapping processes from both of the surface and bulk deep traps, demonstrating the feasibility of using on-chip generated photons to improve the dynamic performances of AlGaN/GaN power HEMTs.

We investigated the threshold voltage (V TH) shift in p-GaN gate AlGaN/GaN power HEMTs under both forward and reverse gate bias conditions at different temperatures. With increasing forward gate bias, the V TH first positively shifted and then decreased. While at the reverse gate bias, V TH shifts monotonically increased towards the positive direction. Positive V TH shifts were due to electron trapping while its decrease was attributed to the optical pumping by the internal electroluminescence (EL). The EL emission from the p-GaN gate region was captured. A light illumination test was performed to verify the effectiveness of optical pumping.

In this work, by using an on-chip Schottky-on-heterojunction light-emitting diode (SoH-LED) which is seamlessly integrated with the AlGaN/GaN high electron mobility transistor (HEMT), we studied the effect of on-chip light illumination on the de-trapping processes of electrons from both surface and bulk traps. Surface trapping was generated by applying OFF-state drain bias stress, while bulk trapping was generated by applying positive substrate bias stress. The de-trapping processes of surface and/or bulk traps were monitored by measuring the recovery of dynamic on-resistance Ron and/or threshold voltage Vth of the HEMT. The results show that the recovery processes of both dynamic Ron and threshold voltage Vth of the HEMT can be accelerated by the on-chip SoH-LED light illumination, demonstrating the feasibility of fully integrated opto-HEMTs to minimize the influences of traps during the dynamic operation of AlGaN/GaN power HEMTs.