Schottky barrier modification on InP using shallow implant layer

Enhanced Schottky barriers are formed on n-InP, using a shallow doped surface layer of type opposite to that of the substrate. The doped surface layer helps in retarding the surface fields, resulting in larger Schottky barrier heights. The Schottky barrier height is found to increase by as much as 0.30–0.35 eV, which is one of the highest that has been obtained for Al/n-InP. Also, the reverse leakage current is reduced by almost three orders of magnitude. However, the ideality factor, at low current levels, is found to be slightly greater than unity (≈1.2). To demonstrate the versatility of our process, the same technique is applied to p-InP samples. As expected, the barrier height is reduced by almost 0.5 eV. The ideality factor for p-type Schottky diodes is found to be very close to unity (≈1.02-1.05) over the entire range of beryllium dosage. The sum of the two Schottky barrier heights is also found to be quite close to the theoretical value of energy bandgap for InP.