Thermally stable PtSi Schottky contact on n-GaN

Abstract

Platinum silicide (PtSi) and Pt Schottky contacts on n-GaN have been investigated and compared. The PtSi contacts were formed on n-GaN by annealing a multilayer structure of Pt/Si with the appropriate thickness ratio at 400 °C for 1 h in forming gas. The barrier height of the as-formed PtSi contacts was found to be 0.87 eV capacitance–voltage (C–V), and remained unchanged after further annealing at 400 and 500 °C. Upon annealing at 600 °C for 1 h, the barrier height decreased to 0.74 eV (C–V), but the diodes remained well-behaved. The as-deposited Pt yielded a barrier height of 1.0 eV (C–V). Upon annealing at 400 °C for 1 h, the Pt diodes degraded and most of the diodes did not survive additional annealing at 400 °C for longer times. The electrical measurements and the Rutherford backscattering spectrometry results indicated that PtSi contacts are thermally much more stable than Pt contacts on GaN.

Thermal reaction of Pt film with 〈110〉 GaN epilayer

“…Similarly, Liu et al observed a degradation of Pt diodes without visible changes in the backscattering spectrum after annealing at 400°C for 1 h in a N 2 flow. 19 These authors further report the appearance of bubbles on the Pt surface after 2 h. Duxstad et al report on small particles of Pt on the surface of the Pt film after thermal treatment in flowing N 2 at 600°C for 30 min. 17 We observe the formation of blisters after vacuum annealing at 550°C for 30 min, and more so at 650°C ͑see also Fig.…”

“…Platinum with its high work function of 5.65 eV 20 exhibits ideal Schottky behavior on n-type GaN with a high barrier height. 15,21 A GaN metal-semiconductor field effect transistor ͑MESFET͒ with Au/Pt as Schottky gate is reported to withstand heating in nitrogen at 400°C for 1000 h. 22 Other authors, though, report the degradation of Pt diodes after annealing at 400°C for 1 h. 19 Low-resistance, ohmic contacts to p-type GaN are achieved by using metals with a high work function, 8 and indeed, Pt or Pd yield a lower value of the total resistance compared to other metals. [7][8][9][10] Platinum is not stable with GaN.…”

“…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.…”

High temperature characterization of Pt‐based Schottky diodes on AlGaN/GaN heterostructures

“…Barrier height values of as-deposited Pt and Pt/Au contacts on GaN in the 0.88-1.08 eV range extracted from I-V measurements have been reported [5][6][7]. Higher values are obtained from capacitancevoltage measurements: 1.16 eV [6] and 1.18 eV [4] for Pt and Pt/Ti/Au contacts, respectively.…”

Metal contacts to n-type GaN

“…Much work has been done already to discover the nature of metal/GaN Schottky contacts. [1][2][3][4][5][6][7][8][9][10][11][12] However, most of these works describe the Schottky diode characteristics for only one or two metals, and none encompass more than four metals. Comparisons between works can be misleading due to great differences in the measurement techniques, the GaN epilayer quality, carrier concentration, and surface preparation before metal deposition.…”