PREPARATION AND CHARACTERIZATION OF SEMIINSULATING 2-IN INP WAFERS HAVING A LOW FE CONTENT BY WAFER ANNEALING

The preparation of nominally undoped semi-insulating (s.i.) InP by hig h-temperature annealing under a controlled phosphorus atmosphere provi des an effective means to improve InP substrate quality. As reproducib le results are restricted to the use of high-purity starting material which cannot be produced with satisfactory yields, the process was app lied to InP predoped with a low Fe concentration ([Fe] approximate to 4 x 10(15) cm(-3)). Since the net donors are only partly compensated, this starting material shows normal semiconducting properties. Wafers (2 in) of this material with a low Fe content were converted to the s. i. state by annealing under a P pressure of 1 atm. The lateral uniform ity was analysed by mapping the resistivity distribution and room-temp erature photoluminescence. The results show that annealed s.i. 2 in wa fers provide a lateral uniformity that could be achieved up to now in as-grown s.i. InP:Fe only by considerably higher Fe doping.