Electerical Engineering, Tarbiat Modarres University
P-type GaAs/AlAs distributed Bragg mirrors have been grown using molecular beam epitaxy on (100) and (311)A GaAs substrates in a similar conditions. A comparison of I-V measurements shows that the resistance of the ungraded mirrors grown on the (311)A substrate is 35 times lower than those grown on the (100) substrate with similar structure. The effective barrier heights for both (311 )A and (100) barriers were extracted from their Arrhenius behaviour, obtained from their current temperature dependence. The calculated values for (311)A and (100) effective barrier heights are 141 meV and 341 meV, respectively. The room temperature values of the specific differential resistance for both devices around zero bias [i.e. Rc=(dV/dJ)Iv=0] were calculated. The approximated values for (311)A and (100) devices are 80 mW-cm2 and 2.8mW-cm2 respectively.