Electroluminescent characteristics of InGaAsSb/GaAlAsSb heterostructure Mid-IR LEDs at high temperatures

The electroluminescent characteristics of an InGaAsSb/GaAlAsSb heterostructure LED emitting at 1.85 $\mu$m are studied in the temperature range 20–200$^\circ$C. It is shown that the emission power exponentially drops as $P\cong$ 0.4 $\exp$(2.05 $\times$ 10$^3$/T) with a rise in temperature primarily because of an increase in the Auger recombination rate. It is found that band-to-band radiative recombination goes in parallel with recombination through acceptor levels, the latter causing the emission spectrum to broaden. With a rise in temperature, the activation energy of the acceptor levels decreases by the law $\Delta E\cong$ 32.9 – 0.075T and the maximum of the LED’s emission spectrum shifts toward the long-wavelength range ($h\nu_{\mathrm{max}}$ = 0.693–4.497 $\times$ 10$^{-4}$ T). Based on the dependence $E_g=h\nu_{\mathrm{max}}-1/2 kT$ and experimental data, an expression is derived for the temperature variation of the bandgap in the Ga$_{0.945}$In$_{0.055}$AsSb active area, $E_g\cong$ 0.817–4.951 $\times$ 10$^{-4}$ T, in the range 290 K $<T<$ 495 K. The resistance of the heterostructure decreases exponentially with rising temperature as $R_0\cong$ 5.52 $\times$ 10$^{-2} \exp$ (0.672/2 $kT$), while cutoff voltage $U_{\mathrm{cut}}$ characterizing the barrier height of a $p$–$n$ junction decreases linearly with increasing temperature ($U_{\mathrm{cut}}$ = -1.59T + 534). It is found that the current through the heterostructure is due to the generation-recombination mechanism throughout the temperature interval.