InGaAs metamorphic laser (λ=1064 nm) power converters with over 44% efficiency

Abstract

The topic of the work is the metamorphic InGaAs heterostructure for laser power converters (LPC) with λ=1064 nm. Epitaxial structures were created by the MOVPE and based on the In0.24Ga0.76As active area grown over a metamorphic buffer (MB) on GaAs-n substrates. The developed technology allows talking about suppression of threading dislocations in the photoactive area from the MB, according to the TEM investigation. The measured spectral dependences of LPCs with different thicknesses of the base layer were investigated by the method of model analysis, and the diffusion length values of minority charge carriers in photoactive layers were determined (2-4 µm depending on the presence or absence of an electric field in the base). Dependences of the dark diffusion saturation current on base thickness were calculated based on minority charge carrier (MCC) diffusion lengths. They show good correlation with experimental values measured from dependences of the open circuit voltage on the incident radiation power. As a result, LPCs based on In0.24Ga0.76As metamorphic heterostructures with and without embedded electric field demonstrate over 44% efficiency for both uniform illuminations (Xe-lamp) and 1064 nm high-power laser radiation at the wide power range (46.8% maximal value for LPC with “optimized” base under uniform illumination). Calculated with taking into account maximal MCC diffusion length and optimal antireflection coating efficiencies show potential of developed metamorphic technology on the level over 50%.