Evolution of the electron localization in a nonconventional alloy system GaAs1−xNx probed by high-magnetic-field photoluminescence

Abstract

We demonstrate that a high magnetic field can be used effectively not only to probe the nature of the photoluminescence ͑PL͒ in a semiconductor, but also to reveal emission peaks that are unobservable at zero field since the magnetic field can alter energy relaxation processes and the statistical distribution of the photocarriers. Our systematic magneto-PL study of GaAs 1Ϫx N x (0.1%рxϽ2.5%) in fields up to 30 T indicates that the character of the low-temperature PL in this system changes drastically with varying nitrogen composition x and exhibits transitions with applying strong magnetic fields. For xϽ0.7%, the PL spectrum shows many discrete features whose energies remain nearly stationary up to the highest applied field. However, the magnetic confinement gives rise to a feature emerging on the higher energy side of the zero-field spectrum. This feature does show a diamagnetic shift, but it is much slower that that of the GaAs band-edge transition. For xϾ1%, the PL spectrum evolves into a broad band, and its diamagnetic shift resembles the band-edge transition in a conventional semiconductor, and the rate of shift is comparable to that of GaAs. From the diamagnetic shift of the band, the reduced effective masses for different composition of nitrogen have been derived for this system using the standard theory for the magneto-exciton in a three dimensional semiconductor.

Effects of heavy nitrogen doping in III–V semiconductors – How well does the conventional wisdom holdfor the dilute nitrogen “III–V‐N alloys”?

“…Magneto-PL has frequently been used for extracting the electron effective mass or reduced mass. In GaAs 1-x N x , quite different results have been obtained in the most recent studies [35,39]. It appears that the PL peak, even under very high field (e.g., B > 30 T), might not actually originate from the band gap transition [35,40], due to the energy relaxation and the existence of various N related bound states.…”

“…In GaAs 1-x N x , quite different results have been obtained in the most recent studies [35,39]. It appears that the PL peak, even under very high field (e.g., B > 30 T), might not actually originate from the band gap transition [35,40], due to the energy relaxation and the existence of various N related bound states. The results of using various other techniques, quantum confinement [6], ODCR on quantum well samples [17] and thermo-magnetic transport [18], are all subjected to further investigation as to what has really been measured.…”

“…The contradiction can easily been understood by noting that the calculated bound states have much larger binding energies (~100 meV) than those for X 1 and X 2 (<20 meV) due to the inadequate accuracy of the impurity potential in the empirical pseudopotential approach. A recent magneto-PL study [35] of GaAs 1-x N x with x > 0.1 % also indicates that the nitrogen induced bound states may have different degrees of localization, depending on how close energetically each bound state is to the host-like band gap.…”

Electronic structure of and SnO under pressure

“…The value obtained for x near 0.01 agrees well with our calculations. The work by Wang et al [39] cites three experimental masses (Fig. 5(d)), but a clear trend cannot be deduced.…”

Interaction between conduction band edge and nitrogen states probed by carrier effective-mass measurements inGaAs1−xNx

“…14 A nonmonotonic dependence of the exciton effective mass was also reported around x = 1.5% in three samples only, and qualitatively ascribed to an interaction between the band edge and N levels. 6 In this work, we measure by magnetophotoluminescence the electron effective mass for N concentrations ranging from a very dilute limit to a full alloy limit. More than 20 samples, both as-grown and hydrogenated, were investigated in order to get an accurate description of the dependence of m e on N concentration.…”