EFFECT OF MELT STOICHIOMETRY ON ELECTRICAL ACTIVATION UNIFORMITY OF SI-IMPLANTED LAYERS IN UNDOPED SEMI-INSULATING GAAS

The effect of melt stoichiometry on the carrier profiles in Si-implanted layers has been investigated for undoped, semi-insulating LEC GaAs grown from melts of different compositions. The electrical activation efficiency tends to increase as the crystals become As-rich. The carrier profile uniformity of the implanted layer across the wafers also depends on the melt stoichiometry. The most uniform distribution of the carrier profiles is obtained for GaAs ingots grown from melts of nearly stoichiometric composition (x equals 0. 499 to 0. 505). These results demonstrate the importance of stoichiometry control in reproducible LEC growth of GaAs which permits formation of electrically uniform Si-implanted layers.