Photoluminescence of a staggered In0.5Ga0.5P/AlxGa1−xAs heterojunction

Abstract

Photoluminescence of the In0.5Ga0.5P/AlxGa1−xAs heterojunction with Al mole fractions x=0.29 and x=0.19 is presented. Below-band-gap photoluminescence with a peak energy less than both band gap energies of the constituent materials was observed. As the laser excitation intensity was decreased, the peak energy of the luminescence shifted to the lower energy side and showed a saturation behavior. The full width at half maximum of the peak also decreased as the laser excitation intensity was decreased. These phenomena indicate that the heterojunction has a staggered band alignment at each value of the Al mole fractions. The expected band alignment of the heterojunction at various Al mole fractions is presented.

Determination of Al mole fraction for null conduction band offset in In0.5Ga0.5P/AlxGa1−xAs heterojunction by photoluminescence measurement

“…Large shift in the peak energy has been attributed to the recombination of spatially separated electrons and holes. 8 The inset in Fig. 2 describes the radiative recombination processes responsible for the luminescences.…”

“…8 It is well known that In 0.5 Ga 0.5 P/GaAs has a straddling band alignment, where both conduction and valence bands of InGaP encompass those of GaAs, although the value of the band offset has been controversial. [9][10][11][12][13][14][15][16] So the band alignment type of the In 0.5 Ga 0.5 P/Al x Ga 1Ϫx As heterojunction is expected to shift from a straddling alignment to a staggered one as the Al content increases from GaAs.…”

Recombination dynamics in n-AlxGa1−xAs/n-In0.5Ga0.5P type-II heterostructures

“…1,2 This heterojunction system can exhibit either a type-I ͑straddling͒ or a type-II ͑stag-gered͒ band line-up depending on the Al composition x in Al x Ga 1Ϫx As. 3,4 The type of band line-up and the value of the conduction band offset in the Al x Ga 1Ϫx As/In 0.5 Ga 0.5 P heterojunction system determined by the capacitance-voltage (C -V) profile technique show that the band line-up crossover between types I and II occurs at xӍ0.…”