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Different Isolation Processes for Free-Standing GaN p-n Power Diode with Ultra-High Current Injection
摘要： In this article, we report on the fabrication and high performance of power p-n diodes grown on free-standing (FS) GaN substrate. The key technique to enhance the high breakdown voltage and suppress the surface leakage current is the isolation process. The mesa-structure diode is generally formed by utilizing the inductively coupled plasma reactive ion etching (ICP-RIE); however, it always induces high surface damages and thus causes a high leakage current. In this study, we propose a planar structure by employing the oxygen ion implantation to frame the isolation region. By following the crucial process, the fabricated mesa- and planar-type diodes exhibit the turn-on voltages of 3.5 and 3.7 V, specific on-resistance (RONA) of 0.42 and 0.46 mΩ-cm2, and breakdown voltage (VB) of 2640 and 2880 V, respectively. The corresponding Baliga’s figures of merit (BFOM, i.e., VB2/RONA) are 16.6 and 18 GW/cm2, respectively. The BFOM of 18 GW/cm2 is the highest reported value for FS-GaN diode. From the temperature dependent measurements, the planar-type diode also shows the better leakage current and thermal stability than the mesa-type diode.
关键词： leakage current,Baliga’s figure of merit,breakdown voltage,planar diode,implantation,GaN substrate
更新于2025-09-23 15:22:29
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Effects of interfaces and current spreading on the thermal transport of micro-LEDs for kA-per-square-cm current injection levels
摘要： The three-dimensional thermal characteristics of micro-light-emitting diodes (mLEDs) on GaN and sapphire substrates were studied with forward-voltage methods, thermal transient measurements, and infrared imaging. The mLEDs on the GaN substrate showed an approximately 10 °C lower junction temperature and smaller amplitude of the K factors than those on the sapphire substrate under the current injection level of 4 kA cm?2. The thermal transient measurement showed that the spreading thermal resistances of the mesa, the GaN epilayer, and the interface of the GaN/substrate were reduced significantly for mLEDs on the GaN substrate because of the high-quality GaN crystal and the interfaces. The infrared thermal images showed lower total average junction temperatures and more uniform temperature distributions for the mLEDs on the GaN substrate, which were also simulated with APSYS software. The thermal transport mechanisms are discussed for the lateral and vertical directions in the mLEDs.
关键词： sapphire substrate,micro-light-emitting diodes,GaN substrate,junction temperature,thermal transport,infrared imaging,APSYS simulation
更新于2025-09-11 14:15:04
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Vertical GaN n-channel MISFETs on ammonothermal GaN substrate: Temperature dependent dynamic switching characteristics
摘要： Switching of GaN-based vertical-trench gate MISFET on ammonothermal n-type GaN substrate are studied as a function of temperature. Pulsed ON-state IV characterization revealed three unexpected independent effects. First, drain current increases with temperature, although electron mobility decreases with temperature. Second, drain current decreases with pulse length, which cannot be explained by heating. Third, dynamic RON increases with OFF-state drain bias, which usually is considered as an issue of lateral GaN HFETs only. The drain current temperature dependence is most likely dominated by the low electron mobility in the inversion layer beneath the gate. The field effect channel mobility is estimated as < 10 cm2/V s and can thus be considered as trap limited and thermally activated, RON decreases from 133 Ω mm at 20 °C to 62 Ω mm at 110 °C. Longer ON-state pulses lead to negative charging of the ALD-Al2O3 gate oxide and shift the threshold voltage (DC-Vth ~8 V) positively. With the maximum applicable Vgs = 10 V, the drain current is not saturated yet and Ids thus drops by a factor 2 when increasing the ON-state pulse width from 0.2 μs to 20 μs due to the Vth-shift. The observed 10-times dynamic RON increase with OFF-state drain bias up to 30 V can be related to possible charging mechanism in the gate oxide as well. Activation energies for different OFF-state stress voltage are ranged linear between 0.08 eV and 0.26 eV for drain bias stress of Vds = 0 V and 30 V respectively.
关键词： Vertical GaN MISFET,Dynamic switching,Ammonothermal GaN substrate
更新于2025-09-10 09:29:36