Free-standing gallium nitride Schottky diode characteristics and stability in a high-temperature environment

Abstract

Schottky diodes have been fabricated using low-resistivity n-type free-standing GaN substrates with a reduced defect density lowly doped n-type epi-layer and an Ni/Ti/Pt/Au Schottky contact metalization. A thermionic field emission current transport mechanism was identified with a Schottky barrier height of about 0.75 eV and a diode ideality of 1.1 measured at 25 • C, both of which increase with measurement temperature up to 200 • C. The diodes were subjected to long-term testing under forward current (1.3 A cm −2 ) or reverse voltage (−3.5 V) biased storage at 300 • C in N 2 for 466 h and were also monitored under non-biased storage conditions for up to 1000 h at 350 • C and 400 • C in N 2 or at 300 • C for 1500 h in air. Except for the non-biased storage test at 400 • C, the diodes show <10% drift in ideality and barrier height during the long-term storage tests. For the 400 • C test, there is a significant increase in both barrier height and ideality over a relatively short storage period (48 h). This to be the first reported study on the long-term stability of Schottky diodes on free-standing GaN and while no catastrophic (e.g. thermal runaway) degradation of any of the diodes was observed, it is proposed that optimized thermal annealing of the Ni-based Schottky contact metalization in the temperature range 350-400 • C is necessary for stable long-term operation at high temperature.

Electrical and microstructural properties of thermally annealed Ni/Au and Ni/Pt/Au Schottky contacts on AlGaN/GaN heterostructures

“…the optimal temperatures for highest SBHs [39][40][41][42]. There was a significant increase of Ni/ Ti/Pt/Au's SBH at an annealing temperature of 400 °C [39].…”

“…Hence, the degradation of the Ni/Pt/Au metallization can be attributed to the presence of It has been reported that Ni/Ti/Pt/Au, Ni/Mo, and Ni/Au Schottky contacts on n-type GaN under thermal annealing have the similar trends, i.e. the optimal temperatures for highest SBHs [39][40][41][42]. There was a significant increase of Ni/ Ti/Pt/Au's SBH at an annealing temperature of 400 °C [39].…”

Review of using gallium nitride for ionizing radiation detection

“…Research by Luther et al 120 showed that Pt Schottky contacts can maintain at 400 C for 500 h without degradation. O'Mahony et al 119 studied Ni-based Schottky contacts and found that under a forward current of 1.3 A/cm 2 or a reverse bias of À3.5 V while stored at 300 C in an N 2 environment for 466 h, the diodes exhibit a drift of less than 10% in both the ideality factor and barrier height. Despite these cases, more research is still needed to understand the long-term operating performance.…”

Low Temperature (180°C) Growth of Smooth Surface Germanium Epilayers on Silicon Substrates Using Electron Cyclotron Resonance Chemical Vapor Deposition

“…Its high carrier mobility and active optical properties have made germanium (Ge) be considered as a promising material for semiconductor devices. There are a number of fledgling technologies being developed that require the epitaxial growth of Ge films on crystalline silicon (c-Si) substrates, such as Ge on Si photodetectors for near infrared (1.3-1.55 m) sensing [8][9][10], Ge lasers [11], and monolithic integration of III-V compound semiconductor devices on c-Si 2 International Journal of Photoenergy [12][13][14][15]. However, the difficulty of growing epitaxial Ge on a Si substrate lies in the 4.2% lattice mismatch between Ge and Si.…”