Temperature dependence of the band gap and comparison with the threshold frequency of pure GaAs lasers

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Abstract
Recent measurements of the lasing energy as a function of temperature in high‐purity GaAs lasers have attempted to investigate the relation between this energy and the one‐electron band gap. Because of a lack of precision in the position of the band gap at high temperature, these measurements show strongly conflicting results. In this work, we report two sets of differential reflectivity measurements (electroreflectivity and piezoreflectivity) performed on GaAs under high‐resolution conditions. Both series of results give for the excitonic absorption edge at room temperature a value E0=1.424±0.002 eV which is about 20 meV higher than the lasing energy reported for the highest‐purity GaAs samples. This result confirms that the lasing energy in GaAs is well below the one electron band gap. In addition, we show that this energy separation is an increasing function of temperature. Finally we discuss a simple model of band‐to‐band recombination including electron‐electron interaction effects and we show that it permits calculation of a temperature dependence of the lasing line in the range 80–300 °K which is in good agreement with the experiment.