Optical Properties of GaNAs and GaAsSb Semiconductors
GaNAs和GaAsSb半导体的光学性质研究（英文）

Under short pulse laser excitation,it has been observed,for the first time,a new high-energy photoluminescence emission from GaN_ x As_ 1- x /GaAs SQWs.This new emission has totally different optical properties compared with the localized exciton transition in GaN_ x As_ 1- x ,and is attributed to the recombination of delocalized excitons in QWs.At the same time,a competition process between localized and delocalized exciton emissions in GaN_ x As_ 1- x /GaAs quantum wells is observed in the temperature-dependent PL spectra under the short pulse excitation. This competition process for the first time,reveals the physical origin of the temperature-induced S-shaped PL peak shift,which was often reported in the disordered alloy semiconductor system under continuous-wave excitation and puzzled people for a long time.We have also investigated a set of GaN_ x As_ 1- x samples with small nitrogen composition( x <1%)by PL,and time-resolved PL.After the PL dependence on temperature and excitation power and PL dynamics were measured,the new PL peak was identified as an intrinsic transition of alloy,rather than N-related bound states.This is the first observation in PL,showing that alloy state exists in GaN_ x As_ 1- x materials even when N composition is smaller than 0.1%. Finally by selective excitation,both type-I and type-II transitions were observed simultaneously in GaAs_ 1- x Sb_ x /GaAs SQWs for the first time.