InxGa1−xAs ohmic contacts to n-type GaAs with a tungsten nitride barrier

Abstract

Significant reduction of the contact resistance of In0.TGaoaAs/Ni/W contacts (which were previously developed by sputtering in our laboratory) was achieved by depositing a W2N barrier layer between the Ni layer and W layer. The In07Gao.sAs/Ni/W2N/W contact prepared by the radio-frequency sputtering technique showed the lowest contact resistance of 0.2 ~mm after annealing at 550~ for 10 s. This contact also provided a smooth surface, good reproducibility, and excellent thermal stability at 400~ The polycrystalline W2N layer was found to suppress the In diffusion to the contact surface, leading to improvement of the surface morphology and an increase in the total area of the InxGa>~As between metal and the GaAs substrate. These improvements are believed to reduce the contact resistance.

Development of InxGa1−xAs-based ohmic contacts for p-type GaAs by radio-frequency sputtering

“…1. 4 Isothermal annealing at 400°C after contact formation was performed for the contact which was deposited on the GaAs substrate etched at a depth of 100 nm and annealed at 550°C for 10 s. The R c values are constant for 5 h and slightly increase after annealing for 10 h as shown in Fig. The diffusion depth of the contact metals after annealing at 550°C for 10 s was measured to be about 50 nm.…”

“…4 The measured R c values are plotted by a solid curve in Fig. These samples were prepared by annealing at 550°C for 10 s (note that this annealing condition provided the lowest R c value for n-type GaAs).…”

“…4 The measured R c values are plotted by a solid curve in Fig. 4 Therefore, the hole concentration at the metal/semiconductor (M/S) interface of the contact prepared on the p-GaAs without etching is not sufficiently high to provide low contact resistance. 1.…”

“…For junction field-effect transistor (JFET) devices, ohmic contacts are required for both n and p-GaAs. These contacts provided low R c value (~0.2 Ω-mm) and were thermally stable after annealing at 400°C for 5 h. 4 These excellent contact properties were concluded to be due to formation of an In x Ga 1-x As layer with high melting point at the metal/GaAs interface, which reduced the Schottky barrier height at the metal/n-GaAs interface. 1,2 These contacts provide low contact resistances (R c ) and good reproducibility.…”

Effects of intermediate semiconductor layers on carrier transport mechanisms through p-ZnSe/metals interfaces

“…8 Recently, thermally stable, low resistance InGaAs/Ni/W 2 N/W ohmic contact to n-GaAs was also developed by forming the intermediate In x Ga 1-x As layer. 9 We have previously explored a possibility to reduce the SBH by forming an intermediate layer at p-ZnSe/metal interface and found that Cd reacted with ZnSe after annealing at temperatures higher than 250°C, forming a Cd-rich Cd x Zn 1-x Se (x≥0.9) layer epitaxially grown on the ZnSe. 10,11 However, no ohmic J-V behavior was obtained.…”