High-voltage mesa-structure GaN Schottky rectifiers processed by dry and wet etching

Abstract

We have fabricated and investigated high-voltage GaN vertical Schottky-barrier rectifiers grown by metalorganic chemical vapor deposition. A mesageometry Schottky-barrier rectifier having a 5-μm-thick i region, and processed using reactive-ion etching, exhibited a reverse breakdown voltage of −450 V (at 10 mA/cm2) and an on-resistance of 23 mΩ cm2. For comparison, we have also applied wet chemical etching for the fabrication of mesageometry Schottky-barrier rectifiers. The 2-μm-thick i-region GaN mesa-Schottky rectifiers showed a breakdown voltage of −310 and −280 V for wet-etched and dry-etched devices, respectively, and an on-resistance of 8.2 and 6.4 mΩ cm2, respectively. These results indicate that the performance of the wet-etched rectifiers is comparable to or better than that of comparable dry-etched devices.

Growth of thick, continuous GaN layers on 4-in. Si substrates by metalorganic chemical vapor deposition

“…While complex group III-nitride (III-N) structures and devices, such as lasers [10], light emitting diodes [2,11], Bragg mirrors [12], acousto-optical waveguides [13] and field effect transistors [1][2][3][4][5][6][7]9,[14][15][16][17][18][19][20] have been demonstrated on silicon, high-volume demand is felt for GaN power rectifiers [21,22]. If a Schottky barrier is used for current rectification, the two major requirements for device epitaxy are: (i) the growth of a low n-type doped GaN layer of 3-6 mm (depending on its free carrier concentration) thickness, and (ii) the growth of an n + -type doped GaN contact layer [22][23][24][25][26]. However, taken alone the different thermal expansion coefficients of GaN (5.59 Â 10 À 6 K À 1 ) and of silicon (2.59 Â 10 À 6 K À 1 ), the cool down from epitaxy to room temperature (RT) causes an in-plane dilatation (e 1 ) of the GaN lattice constant a, which according to the following equation…”

Improved free-standing GaN Schottky diode characteristics using chemical mechanical polishing

“…Schottky rectifiers are a key element of inverter modules because of their high switching speeds and low switching losses, which are important for improving the efficiency of inductive motor controllers and power supplies. In particular, GaN power diodes needed for inverter modules exhibit on-state resistances several orders of magnitude lower than comparable Si devices along with much larger electric field breakdown strengths [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. One of the remaining critical requirements for commercialization is the need for improved Schottky contacts on n-type GaN and AlGaN.…”

Design of edge termination for GaN power Schottky diodes

“…Thus, GaN appears to be an excellent choice for high-power electronics for use in hybrid electric vehicles, power conditioning in large industrial motors, and power distribution and switching. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The Johnson and Baliga power figure-of-merits for both GaN and SiC are several orders of magnitude larger for these applications than is Si. Schottky rectifiers are attractive because of their fast switching speed, which is important for improving the efficiency of inductive motor controllers and power supplies and also their low turn-on voltages compared to p-n junction rectifiers.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The attributes of GaN relative to Si, which also apply to SiC rectifiers, [14][15][16][17][18][19][20][21][22][23][24] include having a maximum electric-field breakdown strength an order of magnitude larger at a given on-state resistance (R ON ), while the on-state resistance is approximately 400 times lower at a given voltage. Thus, GaN appears to be an excellent choice for high-power electronics for use in hybrid electric vehicles, power conditioning in large industrial motors, and power distribution and switching.…”