Study of the emission extraction efficiency of mesa-LEDs with a narrow-gap InAsSb active region

A series of light-emitting diodes (LEDs) (emission peak wavelength $\lambda_{\mathrm{max}}$ = 3.6 $\mu$m) with cone-shaped mesas, which have concave lateral surfaces and heights between 10 to 130 $\mu$m, has been developed. The dependence of the emission efficiency for these LEDs on mesa height has been studied at different injection currents at the temperatures 77 and 298 K. The form of the dependence observed is in agreement with the results of theoretical calculations. It is shown that the effective absorption coefficient, caused by emission extraction from the crystal, may be as large as 3 cm$^{-1}$ for LEDs with the highest mesa (130 $\mu$m) among the diodes in this series. The emission extraction coefficient is close to 30% at the temperature 298 K and 94% at 77 K.