Muneyuki Hirai

Characteristics of Ohmic Contacts to n-Type Boron Phosphide

We grew n-type boron phosphide (BP) (100) on a p-type Si(100) substrate by hydride vapor phase epitaxy. Electrical contacts are important for electrical evaluations and device applications, but the resistivity of ohmic contacts to BP has been little studied. We evaluated the contact characteristics for Al, Au, In, Ti, and Pt by annealing at temperatures in the range 300–500 °C for annealing times up to 50 min using a circular transmission line model pattern. Ohmic characteristics were obtained for the Al, Au, In, and Ti contacts. For the ohmic samples, we calculated the specific contact resistance ρc and observed a metal–BP interface by cross-sectional transmission electron microscopy. The minimum specific contact resistance ρc was 2×10-5 Ω cm2 for the Au/In/n-BP sample annealed at 500 °C for 50 min. For the present samples, thermionic-field emission is considered to be the dominant carrier transport process across the metal–BP interface.

Surface Tension Variation of Silicon Melts with Nitrogen Addition

The surface tension of nitrogen doped silicon melts has been measured as a function of temperature in purified argon atmosphere using the ring tensiometry technique. The absolute value of surface tension decreases at 5% by adding 1017cm-3 nitrogen atoms. The difference increases with increasing the melt temperature. The activation energy of surface tension increases with increasing the nitrogen concentration into the melts. This result suggests the surface energy decrease by adding nitrogen into silicon melts. The surface conditions varies by adding nitrogen into the melts.