Ultra-low leakage and high breakdown Schottky diodes fabricated on free-standing GaN substrate

Abstract

Vertical Schottky diodes were fabricated on the bulk GaN substrate with decreasing impurity concentration from N-face to Ga-face. An array of circular Pt Schottky contacts and a full backside Ti/Al/Ni/Au ohmic contact were prepared on the Ga-face and the N-face of the n-GaN substrate, respectively. The Schottky diode exhibits a minimum specific on-state resistance of 1.3 m cm 2 and a maximum breakdown voltage of 600 V, resulting in a figure-ofmerit of 275 MW cm −2 . An ultra-low reverse leakage current density of 3.7 × 10 −4 A cm −2 at reverse bias of 400 V was observed. Temperature-dependent I-V measurements were also carried out to study the forward and reverse transportation mechanisms.

Characteristics of RF reactive sputter-deposited Pt/SiO2/n-InGaN MOS Schottky diodes

“…Some reported SBHs showed a big change after annealing [6,7,12]; our SBH was relatively stable after annealing at 400 1C. The obtained electrical parameters from our MOS Schottky diode made all by sputtering are compatible to those from MS and MOS devices made by MOCVD and other approaches [2][3][4][5][6][7][8][9][10][11][12].…”

“…However, the development of highquality Schottky contacts to InGaN is very difficult because InGaN layers with a high In concentration will have relatively low carrier mobility and a large amount of surface defects. Ultra-low leakage current is one of the challenges for Schottky contacts to their use in electronic and optoelectronic devices [3][4][5]. MS and MOS Schottky diodes have been considered to be important for electric device applications.…”

“…For forming the Schottky contact, the high work-function metals (Au, Pt, Ni, W, Pd, Ru, Ir, etc.) have been widely used in MS and MOS diodes [2][3][4][5][7][8][9][10]. Several groups have put many efforts to explore MOS Schottky diodes with different methods.…”

Nanoscale conductive pattern of the homoepitaxial AlGaN/GaN transistor

“…The highest quality GaN epitaxial layers would ideally be achieved by homoepitaxy using a GaN substrate which is identical in crystal structure, lattice constant and thermal expansion coefficient. This homoepitaxy template can be achieved by means of a freestanding (FS-GaN) crystal, (obtained after the growth and separation of several hundred micrometers of GaN on a foreign substrate), but such FS-GaN layers still contains several types of imperfections such as scratches and/or edge pits [10][11][12][13][14][15][16][17]. The inherent FS-GaN defects extend into the HEMT active layers and may degrade the charge transport mechanisms, particularly increasing the HEMT off-state leakage currents which, in turn, reduces the breakdown voltage.…”

Vertical gallium nitride schottky diodes for power switching applications.

“…These factors are discussed in detail in the following section. The most common vertical device uses an unintentionally doped epilayers are grown using MOVPE or MOCVD [43] on a free-standing bulk HVPE substrate [44]. Both the MOCVD and MOVPE growth techniques result in high background impurity concentrations of carbon(c), oxygen (O) and hydrogen (H).…”