In-vacuum cleaving and coating of semiconductor laser facets using thin silicon and a dielectric

We propose and demonstrate a novel approach to the coating of semiconductor laser facets. In this approach, processed semiconductor lasers are cleaved in a high-vacuum system immediately followed by coating of the vacuum-exposed facet with a very thin Si layer (less than or equal to 100 Angstrom) and a large band gap dielectric (Al2O3) layer. The Si layer is sufficiently thin to avoid the formation of quantized bound states in the Si. GaAs coated with thin Si and Al2O3 have a higher luminescence yield and a lower surface recombination velocity than bare GaAs surfaces as well as GaAs surfaces coated with Al2O3 only. A surface recombination velocity of 3x10(4) cm/s has been obtained using a modified dead layer model for the Si/Al2O3 sample. It is also shown that lasers which are cleaved in vacuum and subsequently coated with Si and Al2O3 have improved properties including an increased threshold for catastrophic optical damage. (C) 1996 American Institute of Physics.