Effect of band shapes on carrier distribution at high temperature

This paper indicates both experimentally and graphically how the distribution of carriers changes above a critical temperature Tc, which is related to the density of states ρ in the band tails. Thus,kT_{c} = E_{0}, whererho = rho_{0} exp (DeltaE/E_{0}). The emission spectrum shifts with changing excitation (band filling) at lower temperatures (T < T_{c}) and stays at a constant value independent of excitation at higher temperatures (T > T_{c}). Experimental results of photoluminescence studies with GaAs crystals show that the quantity E0, obtained from the dependence of the peak energy upon the degree of excitation is the same as the quantitykT'_{c}, obtained from the dependence of the peak energy upon temperature. This is in agreements with the analysis. For lasing diodes, the threshold will increase steeply with increasing temperature above Tc, if the excited carriers are located mostly in the exponential states of the band tail.E_{0} = (10 sim 20)meV and Tc= (120 sim 250degK) are typical for crystals of heavily compensated GaAs.