Direct Bandgap Type-I Ge Quantum Dots/GeSnSi for SWIR and MWIR Lasers

A direct bandgap type-I Ge QDs/Ge 1− y − z Sn y Si z double-heterostructure on Ge 1− x Sn x virtual substrates is proposed for SWIR and MWIR lasers. The Ge 1− y − z Sn y Si z barrier is lattice-matched to Ge 1− x Sn x . The band structures are calculated with different to Sn contents in Ge 1− y − z Sn y Si z and Ge 1− x Sn x . The band edge energies of Ge QDs vary linearly with x , and independent with y . The Γ-valley is below L-valley when x exceeds 7.5%. The ground states of electrons of Γ- and L-conduction band varies with both x and y . High x and y can increase the conduction band offsets and decrease the valence band offsets. Emission wavelengths range from 1.91 to 4.6 μm are achieved from the proposed structure with proper Sn contents. Graphical abstract Emission wavelength of direct bandgap type-I Ge QDs/Ge 1-y-z Sn y Si z on Ge 1-x Sn x VS.