Interfacial reactions between nickel thin films and GaN

Abstract

Thin Ni films on GaN were annealed at temperatures between 400 and 900°C in N 2 , Ar, and forming gas and were analyzed using glancing angle x-ray diffraction and Auger depth profiling. The first indication of an interfacial reaction was found after an anneal at 600°C for 1 h, after which Ga was observed to be dissolved in the face-centered cubic Ni film. The extent of dissolution increased with continued annealing. After annealing at 750°C for 1 hr in either N 2 or Ar, greater intermixing occurred. The reaction product was either Ni 3 Ga or face-centered cubic Ni with dissolved Ga. Annealing at 900°C resulted in the formation of the B2 phase NiGa. It was clear from Auger depth profiles that the reacted film contained significantly more Ga than N and that N 2 gas was released to the annealing environment, even when the samples were annealed in N 2 gas at 1 atm. Thus, a trend of increasing Ga content in the reacted films was observed with increasing temperature. The observed reactions are consistent with the thermodynamics of the Ni-Ga-N system.

Contact Resistance of InGaN/GaN Light Emitting Diodes Grown on the Production Model Multi-Wafer MOVPE Reactor

“…The nitrogen vacancy in turn compensates the acceptor dopants at the metal/p-GaN interface. Several groups have already reported similar findings on these issues [7,8,9]. In addition, the presence of the high resistive Ni 3 N and Ni 4 N phases at the metal-semiconductor interface at the annealing temperature greater than 500 o C can also result in higher contact resistance [10].…”

Thermal reaction of Pt film with 〈110〉 GaN epilayer

“…A significant dissolution of Ga in Ni was also observed as the first step in the reaction of a Ni film with GaN. 18,27 The similarity between Ni and Pt is mentioned further in the following section.…”

“…13 large N 2 pressure burst at 600°C in ultrahigh vacuum. 27 Venugopolan et al observed the release of N 2 gas from the ͗GaN͘/Ni reaction at 750°C in either Ar or N 2 , even when the nitrogen pressure was 1 atm, 18 as opposed to 600°C in vacuum. 27 In the present study, the loss of nitrogen is indicated by blister formation already at 550°C.…”

“…13 Schottky contacts on n-type GaN have not received much attention yet. Au ͑as-deposited͒, 3,14 Pt and Pd, 1,[15][16][17] Ni, 13,18 and PtSi 19 were reported to have rectifying characteristics. Platinum with its high work function of 5.65 eV 20 exhibits ideal Schottky behavior on n-type GaN with a high barrier height.…”

Metal/GaN reaction chemistry and their electrical properties

“…Many studies on the interfacial reactions between metal and GaN have been carried out in the viewpoint of thermal stability [7][8][9]. However, the results are still conflicting, and moreover, important issues such as the nature of the interfacial reactions and microstructures of metal/p-GaN are remaining unclear.…”