FABRICATION OF UNDOPED SEMIINSULATING INP BY MULTIPLE-STEP WAFER ANNEALING

Recently, it was found that undoped semi-insulating InP can be reprodu cibly obtained by wafer annealing at 950 degrees C for 40 h under phos phorus vapor pressure of I atm. Resistivity variation across the 50 mm diameter wafer after this annealing process, however, was in the rang e of 22.5-53.7%. In order to realize the fabrication of undoped semi-i nsulating (SI) InP with uniform electrical properties, multiple-step w afer annealing (MWA) procedure has been applied for the first time. It was found that two-step wafer annealing at 950 degrees C for 40 h und er phosphorus vapor pressure of 1 atm and at 807 degrees C for 40 h un der phosphorus vapor pressure ranging from 30 to 50 atm, was effective in improvement of the uniformity of the electrical properties of undo ped SI InP. By the present MWA, the resistivity variation of 8-12% and the mobility Variation of 2-4% could be obtained for 50 mm diameter w afers.