PROBLEM RELATED TO THE MBE GROWTH AT HIGH SUBSTRATE TEM0PERATURE FORGaAs-Ga1-xAlxAs DOUBLE HETEROSTRUCTURE LASERS

The MBE growth at high substrate temperature (TS ≈ 600°C) is now often used to obtain GaAs and Ga1-xAlxAs layers with improved electrical and optical properties. In the case of GaAs-Ga1-xAlxAs DH lasers, the optimisation of the threshold current density is obtained for increasing TS ; the ultimate value we reached is l,5KA/cm2 for an active layer thickness of 0,16µm However above a critical value of TS ≈ 670°C, an increase of Jth is observed until a non laser emission. This behaviour is related to a specific problem of MBE growth at extremely high substrate temperature, that will be described.