Temperature dependent characteristics of bulk GaN Schottky rectifiers on free-standing GaN substrates

Abstract

The performance of Schottky rectifiers fabricated with dielectric overlap edge termination on epitaxial layers grown on a free-standing GaN template is reported. The power figure-of-merit (VB)2/RON where VB is the reverse breakdown voltage and RON is the on-state resistance was 11.5 MW cm−2. The forward turn-on voltage was ∼3.5 V at 25 °C, with an on-state resistance of ∼5×10−3 Ω cm2. The reverse recovery time was ⩽50 ns in switching from forward bias to reverse bias. The reverse breakdown showed a temperature coefficient of −0.45 V/C.

Structural and optical studies of thick freestanding GaN films deposited by Hydride vapor phase epitaxy

“…Impurity trace analysis of this 14 mm thick film indicates that low background impurity levels were achieved, which is a basic requirement for high breakdown blocking layers in fast switches. This preliminary result is quite encouraging, but numerical calculation indicates that to achieve a 10 kV breakdown voltage, films with 1 Â 10 15 /cm 3 free carrier concentration must have thickness exceeding 50 mm [3]. These relatively large required film thicknesses make difficult the use of deposition techniques such as MOCVD, which has growth rates typically on the order of 2 mm/h.…”

Thick homoepitaxial GaN with low carrier concentration for high blocking voltage

“…defect densities must be reduced. A theoretical calculation for the breakdown voltage of a GaN punch-through diode indicates that over 1000 V can be achieved with a 5 mm thick blocking layer and a donor concentration of 5 Â 10 15 cm À 3 [3]. Experimental results reveal much lower breakdown voltages indicating that processing and growth induced defects are the major contributions for premature breakdown [3].…”

“…A theoretical calculation for the breakdown voltage of a GaN punch-through diode indicates that over 1000 V can be achieved with a 5 mm thick blocking layer and a donor concentration of 5 Â 10 15 cm À 3 [3]. Experimental results reveal much lower breakdown voltages indicating that processing and growth induced defects are the major contributions for premature breakdown [3]. Zhang et al [5] demonstrated that vertical devices fabricated with several microns thick homoepitaxial films reach a figure-of-merit (FOM) as high as 48 MW/cm 2 , exceeding the 15.5 MW/cm 2 value achieved with optimized planar devices.…”

“…Recently, it was demonstrated that GaN Schottky diodes fabricated on freestanding GaN substrates with simple metal overlap edge termination show reverse recovery time less than 50 ns, low on-state resistance, and low negative temperature coefficient of the breakdown voltage [3]. Such characteristics promote GaN as a promising material for the fabrication of fast switching devices to improve the efficiency of inductive motor controllers and power supplies [4].…”

Chemical lift‐off of GaN epitaxial films grown on c‐sapphire substrates with CrN buffer layers

“…1 Introduction Freestading GaN substrates have been used to improve performances of light-emitting devices and high-power devices [1][2][3]. GaN substrates have been fabricated from thick GaN layers grown by hydride vapor phase epitaxy (HVPE) on c-plane sapphire using buffer layers which are followed by the separation of the thick GaN layers from the c-plane sapphire substrates.…”