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In gallium nitride (GaN) lateral power devices with advanced E-field management, isolation becomes a bottleneck for achieving higher breakdown voltage (BV). To understand the physical mechanism of isolation, the experimental analysis of isolation structures is done in this work. This article presents the measured leakage current and breakdown characteristics of isolation structures, compatible with lateral devices. For unimplanted isolation structures, leakage is injection barrier limited and breakdown is by surface punchthrough. BV has a quadratic dependence on the isolation length. Ion implantation introduces trap-limited hopping conduction, marked by the exponentially field-dependent conductance. After implantation, despite an increase in leakage current, BV increases drastically. The dependence of BV on isolation length changes from quadratic in unimplanted isolation to linear in implanted one due to flattening of E-field. To achieve high BV in GaN lateral power devices, the implanted isolation structure is preferred at the cost of high isolation leakage.

Monolithic integration of photodetector and transimpedance amplifier is demonstrated for galvanically isolated control of GaN power switches. The transimpedance amplifier includes a bootstrapping comparator and an optical receiver stage. The bootstrapping comparator features depletion-mode AlGaN/GaN high electron mobility transistors for optimized speed and input common mode range spanning from −1 to 8 V. The comparator delivers a voltage gain up to 176 V/V and a unity-gain bandwidth of 3.58 MHz. Within the optical receiver stage, the photodetector exhibits a photocurrent range of 50 to 100 nA when stimulated by a 340 nm wavelength light emitting diode. Together with a 330 k $\Omega $ pull-up resistor, the optical receiver stage generates a voltage signal ranging from 16.5 to 33 mV. The signal is then amplified by the bootstrapping comparator, resulting in an output voltage signal with a peak-to-peak voltage of 3.1 V, operating at 1 kHz frequency.