The Recombination Mechanism Of Excited-State Acceptor-Acceptor Pairs In GaAs

Recently we found two new emissions denoted by 'g' and [g-g] in the low temperature photoluminescence (PL) spectra of acceptor-impurity incorporated GaAs. 'g is situated at an energy slightly below that of the bound exciton emissions. [g-g] is situated just below 'g' and shows a significant energy-shift towards the lower energy side with increasing acceptor concentration,[A]. Previously we proposed a model in which [g-g] was ascribed to the acceptor-acceptor pair formed by the overlapping of wave functions of the 2p state of the isolated acceptors. Although the calculated energy as a function of [A] showed qualitative agreement with the experimental results, it was always larger than the observed binding energy of [g-g]. In this paper it is indicated that the red shift of [g-g] with increasing [A], and its energy locking at a critical [A], can be well explained by phenomenologically taking into account the screening effect of the hole which is in the ground state. It was explicitly demonstrated that [g-g] is a very useful optical tool for the estimation of [A].