Photoluminescence measurements in Ge-doped p-type Ga0.60Al0.40As

Abstract

Results of photoluminescence and Hall effect measurements of p-type Ge-doped Ga0.60Al0.40As grown by liquid phase epitaxy are reported. The effective segregation coefficient for Ge for growth at 785 °C is estimated to be ∼2×10−3. The photoluminescence spectra at 5.5 K are characterized by two edge emission bands at ∼1.91 and ∼1.88 eV and a broadband at ∼1.55 eV. The edge emission bands are identified to be donor-acceptor pair recombination bands involving the same donor but two different acceptors. The ionization energy of the donor is estimated to be 50–60 meV and the acceptor ionization energies are estimated to be ∼60 and ∼100 meV for the 1.91- and 1.88-eV bands, respectively. The deep acceptor is believed to involve a background impurity, most likely C or Si. It is suggested that the 1.55-eV band arises from a next-nearest neighbor complex consisting of Ge on an arsenic site and an As vacancy. Post-growth annealing treatment at 830 °C is found to decrease the photoluminescence intensity suggesting the presence of annealing induced nonradiative centers.

Broad photoluminescence band in undoped AlxGa1−xAs grown by organometallic vapor phase epitaxy

“…The peak energy is almost constant except for a slight increase at the highest excitation power. This result is also similar to the results for Ge-doped Al 0.4 Ga 0.6 As, 10 suggesting that the luminescent center is similar in nature for both undoped and Ge-doped Al x Ga 1Ϫx As. This constant behavior contradicts the expectations for D-A pair recombination.…”

“…This energy is similar to that of the broad band found in Zn-doped Al x Ga 1Ϫx As ͑1.6-1.7 eV͒, 4,6,9 but slightly larger than that for Ge-doped Al x Ga 1Ϫx As ͑1.5-1.6 eV͒. 8,10 The integrated intensity I PL and the full width at halfmaximum ͑FWHM͒ of the DB band are plotted in Fig. 3 as a function of x. I PL increases with x, reaches a maximum at xϭ0.52, and then steeply decreases for larger values of x.…”

“…I p increases sublinearly with L, which is in agreement with the results for Ge-doped p-type Al 0.4 Ga 0.6 As. 10 Schmidt et al presented a model for the excitation power dependence of the near-bandedge PL intensity, which predicts that sublinear dependence will occur for free-to-bound and donor-acceptor ͑D-A͒ pair recombination. 16 On the other hand, Glinchuk et al presented a model in which the presence of a nonradiative shunt path causes sublinear dependence.…”

“…Up until now, a number of photoluminescence studies have been performed on doped Al x Ga 1Ϫx As grown by organometallic vapor phase epitaxy ͑OMVPE͒ and molecular-beam epitaxy. [1][2][3][4][5][6][7][8][9][10] One of the main subjects in these studies is the deep-level broad emission bands with emitted photon energies of 1.2-1.9 eV that depend on the AlAs mole fraction (x) and their origin. In Si-doped n-type Al x Ga 1Ϫx As, 1.2-1.4 eV bands have been found and attributed to donor-vacancy and other complexes.…”

“…Similar broad bands centered at 1.5-1.7 eV were found and their origins have been investigated from their intensity dependencies on the V/III ratio and on annealing. [6][7][8][9][10] Acceptorvacancy or oxygen-acceptor complexes have been suggested as the origins of the bands, but their origin is still controversial. On the other hand, there have been few systematic PL studies on undoped material.…”