Photoluminescence of undoped bulk InP grown by the liquid-encapsulated vertical Bridgman technique

Abstract

The 4.2 K photoluminescence (PL) spectra of undoped bulk 〈100〉 InP grown by the liquid-encapsulated vertical Bridgman (LE–VB) techniques are characterized by three kinds of recombination peaks. A peak exhibited near band-gap energy is attributed to the recombination of bound excitons (BEs). At the low energy side of BEs, a series of peaks with the same energy interval are due to the recombination of donor–acceptor (DA) pairs with their longitudinal–optical (LO) phonon replicas, which is associated with the Zn acceptor. Recombination of deep levels (DLs) is characterized by a broadband with fine structure at the higher energy side, which seems to be associated with the recombination of native defects and their phonon replicas. The lattice relaxation of DA recombination is smaller while the recombination intensity of DLs is stronger as compared the 4.2 K PL spectra of the LE–VB crystals with those of seed crystals grown by the liquid-encapsulated Czochralski (LEC) technique. At room temperature, only a broadened peak near band-gap energy is recognized in both the LEC seed and as-grown LE–VB crystals, which is assigned as the recombination of band to bands. The PL mapping results show that the recombination intensity of band to bands in the LE–VB crystal is stronger than that in the LEC crystal. By combining the etched pit density analysis, the stronger PL intensity of band to band recombination in the LE–VB crystal is considered to be due to the lower densities not only of native defects responsible for the recombination of DLs but also of dislocations responsible for the etched pit.