IVT measurements of GaN power Schottky diodes with drift layers grown by HVPE on HVPE GaN substrates

Abstract

To date, a majority of epitaxial layers for vertical gallium nitride (GaN) power Schottky diodes have been grown by metalorganic chemical vapor deposition. In this work, we investigate the electrical properties of vertical GaN Schottky diodes with drift layers grown by hydride vapor phase epitaxy (HVPE) on moderately-doped freestanding HVPE GaN substrates. Room temperature IV data is presented for devices tested where results for diode characteristics such as the breakdown voltage, V_b, specific on-resistance, R_on-sp, ideality factor, n, and barrier height, Φ_b, are measured for devices across the 1 cm × 1 cm sample. The smallest diodes, which are 30 μm in diameter, show the smallest specific on-resistance, whereas the breakdown voltage (defined as the voltage corresponding to a current of 10 mA cm⁻²) is independent of device size across the wafer. IV data show an average value of 1.06 ± 0.06 for n and 0.80 ± 0.04 eV for Φ_b with little variation across the wafer, suggesting a reasonable metal–semiconductor interface across the entire sample. For one of the 300 μm devices tested, we also examine the IV properties as function of temperature from 25 to 250 °C in increments of 25 °C and extract a zero temperature Φ_b of 0.908 eV and Richardson’s constant of 4.44 A cm⁻² K⁻² which is significantly less than the theoretical value of 26.9 A cm⁻² K⁻².