Enhancement of the Schottky Barrier Height using a Nitrogen-Rich Tungsten Nitride Thin Film for the Schottky Contacts on AlGaN/GaN Heterostructures

Abstract

Tungsten, stoichiometric W 2 N, and nitrogen-rich W 2 N films were used as Schottky contacts on AlGaN/GaN heterostructures. The nitrogen content in the film was controlled by varying the nitrogen-to-argon gas flow ratio during the reactive sputter deposition. The diode with the nitrogen-rich film exhibited a higher Schottky barrier height and the leakage current was comparable to that of the Ni/Au Schottky contact. Analysis suggested that this was due to the increase of the tungsten nitride work function as the result of higher nitrogen incorporation. Furthermore, after 600°C thermal annealing, the diode was stable and showed no change in the leakage current.

Stable AlGaN/GaN high electron mobility transistors with tungsten nitride gate metallisation

“…The wafer was then split in half and two different Schottky gate schemes of WN x /Au and Ni/Au metal stacks were deposited on separate pieces. The nitrogen-rich WN x /Au metal stacks were deposited as described in [9]. The resulting WN x layer was 100 nm thick.…”

“…Based on our previous study on nitrogen-rich tungsten nitride Schottky diodes that demonstrate a high Schottky barrier height and good thermal stability [9], this Letter presents a WN x gated HEMT device with no sign of degradation from gate forward current stress and which delivers excellent power performance.…”

Novel pseudo-morphotactic synthesis and characterization of tungsten nitride nanoplates

“…As one important member of metal nitrides, tungsten nitrides (W x N) have many promising properties, including good chemical stability, high strength, high hardness, high melting point with good electrical conductivity and a relative low band gap (2.2 eV) [8][9][10]. These unique properties make tungsten nitrides and related tungsten-containing ternary nitrides have wide applications in the following aspects: effective barriers against diffusion of copper in microelectronic circuits [11][12][13], gate electrodes in MOS devices [14], Schottky contacts on AlGaN/GaN heterostructures [15], contact barrier for DRAM [16], wear-resistant coatings [10], contamination resistant coatings [17], photocatalysts for water decomposition using solar light [9], cathode catalysts for fuel cells [18] and catalysts for NO dissociation [19].…”

Gold free contacts to AlGaN/GaN heterostructures

“…The WN x Schottky contact to n-GaN was thermally stable up to 850 o C, and the ideality factor and the barrier height remained at 1.10 and 0.80 eV, respectively after 850 o C annealing. Lu explored enhancement of the Schottky barrier height using a nitrogen-rich tungsten nitride thin film [82]. They have investigated tungsten, stoichiometric W 2 N, and nitrogen-rich W 2 N films as contacts on AlGaN/GaN.…”

“…Lu et al [82] obtained WN x films by reactive DC sputtering, on Al-GaN/GaN heterostructures. The nitrogen content in the film was controlled by varying the nitrogen-to-argon gas flow ratio during the reactive sputtering deposition.…”