Temperature sensitivity (T) of tensile-strained GaAsP/(AlGa)As double-barrier separate confinement heterostructure laser diodes for 800 nm band

Abstract

The temperature sensitivity of the double-barrier separate confinement heterostructure (DBSCH) laser diodes (LDs), intended for high-power, low vertical beam divergence emission, was shown to be somewhat lower than that of the large optical cavity (LOC) devices of similar beam divergences. For the lowest beam divergences, it still remains considerably high, resulting in low characteristic temperatures T0 not exceeding 80 K in the LDs of the vertical beam divergences below 15°. In this work, the decrease in the T0 values of such tensile-strained GaAsP/(AlGa)As DBSCH LDs has been found primarily due to an increased, thermally activated occupation of the heavy-hole subband and, to a minor degree, occupation of the second quantum level, both giving rise to transitions that do not contribute to the optical gain. This is caused by the higher and more temperature-dependent at-threshold band filling for devices of reduced confinement factor (Γ) aimed at achieving low beam divergence. This phenomenon seems to be common for all the tensile-strained LDs and acts in addition to other mechanisms that decrease the T0, such as the carrier escape from a quantum well to surrounding layers. However, in DBSCH LDs no carrier escape has been detected, presumably because of their thin waveguide layers. This can explain the somewhat higher T0 values of these devices when compared to their LOC counterparts.