Excitation Properties of Er-Doped GaP from Photoluminescence and High Pressure Studies

Abstract

AbstractThe photoluminescence properties of MOCVD GaP:Er were investigated as a function of temperature, applied hydrostatic pressure, and excitation wavelength. Four sharp peaks are observed on the high energy side of the 1.54 μm Er3+ emission. These peaks are selectively excited by below-gap energies and have a significantly shorter lifetime than the main Er3+ emission, suggesting that at least two distinct Er3+ centers contribute to the luminescence. The low temperature photoluminescence excitation (PLE) spectrum of the 1.54 μm emission was also measured. Strong broad excitation of the Er3+ centers occurs with energies well below the indirect bandgap energy. In fact, the Er3+ emission intensity is significantly stronger when excited with below-gap wavelengths than with above-gap wavelengths. This result has been explained in terms of competition between Er3+ excitation and nonradiative deep level recombination for free carriers under above-gap excitation. With below-gap excitation, carriers are promoted directly into the Er3+ excitation pathway via absorption at an erbium-related trap. At 42 kbar, below-gap excitation is no longer more efficient than above-gap excitation, suggesting that competitive capture of free carriers by deep levels has been reduced.