Bipolar junction transistors are provided in which at least one of an emitter contact, a base contact, or a collector contact thereof is formed by epitaxially growing a doped SixGe1-x layer, wherein x is 0≦x≦1, at a temperature of less than 500° C. The doped SixGe1-x layer comprises crystalline portions located on exposed surfaces of a crystalline semiconductor substrate and non-crystalline portions that are located on exposed surfaces of a passivation layer which can be formed and patterned on the crystalline semiconductor substrate. The doped SixGe1-x layer of the present disclosure, including the non-crystalline and crystalline portions, contains from 5 atomic percent to 40 atomic percent hydrogen.