Effect of n- and p-Type Doping on the Microhardness of GaAs, (AI,Ga)As and Ga(As, Sb) Active Layers in 0.82 and 0.87 / m Injection Lasers

The effect of n- and p-type doping on the microhardness of the active layers used in the GaAs injection lasers operating at 0.82 and 0:87 ~m, was investigated with the objective to alleviate the dark line degradation problem, particularly in the 0.87 ~m lasers. Consistent with the results in bulk melt grown crystals, n-type doping was found to increase the hardness relative to p-type doping of the (A1,Ga)As (0.82 ~m) and GaAs and Ga(As,Sb) (0.87 ~m) active layers grown by liquid phase epitaxy. In addition, for n-type crystals, Ga(As,Sb) was harder than (A1,Ga)As which in turn was harder than GaAs. The n-type doping effect on hardness did not persist under optical carrier injection conditions. The growth of the plastic zone around the microhardness indentation region, examined by photoluminescence and x-ray topography, was not in any way less for the harder n-type Ga(As,Sb) or (GaAs) compared to p-type material indicating that n-type doping alone of the 0.87 ~m active layers will not be effective in reducing degradation by dark line defects. The 0.82 and 0.87 #m injection lasers required for~ optical communication systems are being fabricated from (A1,Ga)As-GaAs double heterostructures (1). The lasing active layer contains typical ly 8 % A1 (1) for the 0.82 ~,m laser whi le the 0.87 ~m laser can b