CHARACTERIZATION OF PRASEODYMIUM-DOPED INGAP EPILAYER GROWN BY LIQUID-PHASE EPITAXY

Praseodymium (Pr) is added to the InGaP growth melt during liquid phase epitaxy (LPE). The epilayers are grown, by using a supercooling method, on (100) Cr-doped semi-insulating GaAs substrates at a growth temperature of 790-degrees-C. An examination of the structural properties of the InGaP-grown layers reveals that its lattice constant increases slightly with increasing Pr concentration in the growth melts. Similarly, an examination of the electrical properties reveals that, depending on the amount of Pr in the growth melt, n-type InGaP epilayers with room-temperature electron concentrations in the range of 3.4 X 10(16) cm-3 to 5.2 X 10(15) cm-3 and electron mobilities from 730 to 1310 cm2/V s can be prepared. The photoluminescence spectral results show that by increasing the amount of Pr in the growth melt, smaller full-width at half-maximum values and better band-edge emission intensities result. The experimental results support the fact that Pr exhibits a gettering effect in the InGaP LPE process, as no characteristic Pr intra-4f-shell transitions are observed in the luminescence spectra of the InGaP-grown layers.