Defect density reduction of n/sup +/p and p/sup +/n InP structures fabricated by closed ampoule thermal diffusion

A significant reduction of defect densities of n/sup +/p and p/sup +/n InP structures fabricated by closed-ampoule thermal diffusion was obtained after optimizing the diffusion process. For n/sup +/p structures, the lowest etch pit density (EPD) of 6*10/sup 5/ cm/sup -2/ was achieved after S diffusion into InP:Cd (N/sub A/=1.2*10/sup 16/ cm/sup -3/) substrates using a thin In(PO/sub 3/)/sub 3/-rich anodic oxide diffusion cap layer at a diffusion temperature of 660 degrees C, while the lowest EPD after S diffusion into InP:Zn (N/sub A/ approximately 2*10/sup 16/ cm/sup -3/) under similar diffusion conditions was 8*10/sup 6/ cm/sup -2/. For p/sup +/n structures, surface EPD values as low as 4*10/sup 2/ cm/sup -2/ were achieved in the case of Cd diffusion into InP:S (N/sub D/=3.5*10/sup 16/ cm/sup -3/) substrates at a diffusion temperature of 560 degrees C using a thin In(PO/sub 3/)/sub 3/-rich chemical oxide diffusion cap layer, while the lowest EPD in the case of Zn diffusion was 3*10/sup 5/ cm/sup -2/. The differences are explained by the large number of In/sub 2/S/sub 3/, InS, and Zn/sub 3/P/sub 2/ surface and deep precipitates detected in the case of n/sup +/-p(S, Zn) and p/sup +/-n (Zn, S)InP structures.<
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