Using GaN-on-Si epilayers, for the first time, fully vertical p-i-n diodes are demonstrated after Si substrate removal, transfer, and n-electrode formation at the top of the device. After SiO ₂ sidewall passivation, the vertical p-i-n diodes, with n-GaN facing up, exhibit VON of 3.35 V at 1 A/cm ² , a low differential ON-resistance of 3.3 mΩcm ² at 300 A/cm ² , and a breakdown voltage of 350 V. The corresponding Baliga's figure of merit is 37.0 MW/cm ² , a very good value for GaN-based p-i-n rectifiers grown on Si substrates. The results indicate that fully vertical rectifiers using GaN-on-Si epilayers have great potential in achieving cost-effective GaN devices for high-power and high-voltage applications.

An active matrix light emitting diode (LED) micro-display system was demonstrated with GaN-on-Si epilayers and a custom-designed CMOS backplane using an Au-free Cu/Sn-based metal bonding method. The blue micro-LED array consists of $64\times36$ pixels with a pitch size of $40\,\,\mu \text{m}\,\,\times 40\,\,\mu \text{m}$ and a pixel density of 635 pixels/in (ppi). The Si substrate for the LED growth was removed by reactive ion etching (RIE) using SF ₆ -based gas after flip-chip bonding. Crack-free and smooth GaN layers in the display area were exposed. Images and videos with 4-bit grayscale could be clearly rendered, and light crosstalk was significantly suppressed compared to its counterpart using the GaN-on-sapphire epilayers. The demonstration suggests the tremendous potential of the low-cost and large-scale GaN-on-Si epilayers and cost-effective Au-free Cu/Sn-based bonding scheme for micro-display applications.

This paper reports a novel voltage-controlled light emitter with fast switching speed and dimming capability using a monolithically integrated GaN HEMT-LED device. The integrated HEMT-LED device, with a transconductance of 113 mS/mm and large light emitting area (450 ×470 μm2), exhibits a fast switching speed of 15 MHz. When functioning as an optical transmitter, a data rate of 16.7 Mbit/s was demonstrated. By reducing the duty cycle of the pulsed gate voltage from 100% to 0.1%, the light intensity decreased accordingly, and a linear pulse-width modulation (PWM) dimming performance with a wide dimming range (0.1% to 100%) and high dimming ratio (51,282:1) was achieved.

We report lateral integration of an InGaN/GaN light-emitting diode (LED) and an AlGaN/GaN high electron mobility transistor (HEMT) via the epitaxial layers. Direct contact of the HEMT channel and the n-GaN electrode of the LED allows for conversion of a current-controlled LED to a voltage-controlled device by the gate and drain biases. The integrated HEMT-LED exhibited a light output power of 7 mW from the LED with a modulated injection current of 80 mA through the HEMT (V _DD = 8 V and V _GS = 1 V). The off-state breakdown voltage for the integrated HEMT-LED was 530 and 270 V at forward and reverse bias condition, respectively. The superior characteristics are attributed to the common GaN/AlN buffer platform featured with high crystalline quality and large resistivity simultaneously.

We report growth and fabrication of fully- and quasi-vertical GaN-on-Si p-i-n diodes. A record high Baliga figure of merit of 304 and 152 MW/cm ² is reported for fully-and quasi-vertical GaN-on-Si p-i-n diodes, respectively. A comprehensive comparison has been made between the two kinds of diodes in regard ON-resistance, breakdown voltage, and switching performance. An ultralow differential ON-resistance of 0.5 and 1.0 mQ · cm ² has been demonstrated for quasi- and fully-vertical diodes with a diameter of 60 μm at 3 kA/cm ² . Current crowding effect in the n-GaN was a dominant factor of RON, especially for large size quasi-vertical diodes at high current density. A high V _br of 390 V has been demonstrated for the two types of device structures, regardless of device diameters. The same breakdown voltage and low off-state leakage indicated the reliability of fully-vertical device fabrication that reflects intrinsic properties of the grown epilayers. The two kinds of diodes share similar switching performance, which is much superior to a commercial fast-recovery Si diode as a reference. The device characteristics show promising potential of both fully-and quasi-vertical diodes for low-cost high-power applications.