Planar germanium diodes and transistors

A diffusion-mask technique has been developed to make germanium planar diodes and PNP transistors. This preferential masking is effective for various P and N type dopants at different concentration levels and diffusion lengths. A comparison is made of all the characteristics of the planar and its equivalent mesa structure. All the surface dependent parameters, such as diode reverse current, surface recombination velocity, have shown improvement over mesa units. Also, a very narrow distribution of these parameters has been observed. Units fabricated by this technique have higher reliability at ambient as well as elevated temperatures over equivalent mesa units. Life stability of the device is very satisfactory.