Group IV Element PN Junction Light Emitting Diodes

In this thesis, the emission and minority carrier lifetime of monocrystalline Si solar cell and enhancement of direct bandgap transition from Ge np junction LED are discussed.he emission image and lifetime measurement is very useful as a diagnosis tool for solar cells. The infrared emission at the Si band edge is observed from an n+p solar cell and is confirmed by the electron-hole plasma recombination model. The temporal electroluminescence is measured and fitted with the radiative, SRH and Auger recombination mechanisms. The minority carrier lifetime of the value ~1.8 ms is measured.he direct bandgap transition (1.6um) from Ge was observed in the photoluminescence (PL) and electroluminescence (EL) at room temperature. The methods to enhance direct radiative recombination are: (1) electron injection into direct valley by increasing current injection level at forward voltage, (2) increasing device temperature to increase electron population in direct band, (3) using tensile strain to move the direct valley closer to indirect valleys. The direct bandgap transition from Ge can further increase the emission intensity due to higher radiative recombination coefficient as compared to indirect bandgap transition.