Temperature dependence of spontaneous peak wavelength in GaAs and Ga1−xAlxAs electroluminescent layers

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Abstract
We report the results of experiments which determine how the peak wavelength (λp) of the spontaneous emission spectrum shifts with junction temperature (T). The quantity ∂λp/∂T has been measured for homostructure, single−heterostructure, and double−heterostructure LED’s throughout the temperature range 293−413 °K. Particular emphasis was placed on how the presence of Al in a GaAs layer alters ∂λp/∂T. The principal results are as follows: (i) ∂λp/∂T ranges from 2.5 to 3.6 Å/°K for pure GaAs; (ii) ∂λp/∂T is decreased in direct proportion to the aluminum fraction x in Ga1−xAlxAs. An explanation of these results is presented which involves only the known magnitudes and temperature dependences of the direct energy band gaps of GaAs and AlAs; for example, at x=0.3, the calculated reduction is 35% which is in good agreement with the experimental data; (iii) the spectra for some LED’s have two peaks identified with band−to−band (BB) and band−to−acceptor (BA) recombination processes. For the BA peak ∂λp/∂T is 0.5 to 0.6 Å/°K higher and its amplitude decreases much more rapidly with increasing temperature than for the BB peak. This behavior has been explained by a model which takes into account the number of ionized acceptors as a function of temperature.