Extreme reduction of on-resistance in vertical GaN p–n diodes by low dislocation density and high carrier concentration GaN wafers fabricated using oxide vapor phase epitaxy method

Abstract

Low dislocation density and low-resistance GaN wafers are in high demand for improving the performance of vertical GaN power devices. Recently, GaN wafers with the dislocation density of 8.8 × 104 cm−2 and the resistivity of 7.8 × 10−4 Ω cm, were fabricated using oxide vapor phase epitaxy (OVPE). In this study, GaN p–n diodes on GaN wafers prepared by the OVPE method were evaluated for verifying their suitability as vertical GaN power devices. An extremely low-differential specific on-resistance of 0.08 mΩ cm2 and a high breakdown voltage of 1.8 kV were obtained from forward and reverse I–V measurements.

Terahertz time-domain ellipsometry with high precision for the evaluation of GaN crystals with carrier densities up to 1020 cm−3

“…Many III-nitride-based power electronic and optoelectronic devices require high free carrier concentrations, thus the motivation for doping investigations on GaN 4 , 5 . For next-generation power devices, the newly developed vertical GaN transistors, which show great potential for high-current and high-voltage operations, demand GaN wafers with high quality and low resistance 2 , 3 , 6 , 7 . In deep ultraviolet LEDs, GaN-based carrier injection layers with doping concentrations up to 10 19 cm −3 are used 8 , 9 .…”

Breakdown phenomenon dependences on the number and positions of threading dislocations in vertical p-n junction GaN diodes

“…[1][2][3][4][5][6] Since it was difficult to fabricate highquality GaN substrates, the development of GaN devices was performed using GaN grown on heterogeneous substrates such as Si, SiC, and Al 2 O 3 . [7][8][9][10][11][12] In recent years, improvements in substrate quality have been actively promoted, [13][14][15][16][17][18][19] and a low threading dislocation density (TDD) in the range of 10 5 cm −2 has been realized, [20][21][22][23][24][25][26][27][28][29][30] and the development of vertically structured devices which will lead to future highpowered conversion systems has been carried out. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] Among various types of devices, we have e...…”

Low-pressure acidic ammonothermal growth of 2-inch-diameter nearly bowing-free bulk GaN crystals

“…Several methods have been developed to grow GaN crystals, such as hydride vapor phase epitaxy (HVPE), [4][5][6][7][8][9][10][11][12][13] ammonothermal (AT), [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and Na-flux [29][30][31][32][33] methods. The HVPE method involves the reaction of ammonia (NH 3 ) and gallium chloride gases on heteroepitaxial wafers such as Si and sapphire at approximately 1000 °C in a quartz reactor.…”

“…Recently, a replacement of gallium chloride by gaseous Ga 2 O has also been proposed. [9][10][11][12][13] However, HVPE suffers from several disadvantages. For example, the formation of solid-phase byproducts hinders long-term continuous growth, and the crystals grown on lattice-mismatched foreign substrates are in general of high TD density.…”