Germanane is novel 2D graphene analog material. However, in sharp contrast to graphene it exhibits semiconducting properties with direct band gap of 1.50 eV. Germanane exhibits high electron mobility and its alkylation allows band gap tuning from 1.50 eV for allyl to 1.62 for methyl germanane. The semiconducting properties of alkylated germanane make them suitable for application is photocatalysis, optoelectronic, sensing etc.