Ga(As)Sb/GaAs quantum dots for emission around 1300 nm

Abstract

Summary form only given. We report on Ga(As)Sb/GaAs quantum dots (QDs) for use in efficient QD lasers. The emission wavelength can be chosen with the variation of the growth temperature and the Sb/Ga V/III partial pressure flux ratio. As can be seen from the experimental photoluminescence (PL) results the emission wavelength can be shifted in a wide range between 876 and 1035 nm. The nominal coverage of 3 monolayers (ML) is constant. A higher Sb flux causes bigger quantum dots with a higher Sb concentration within the dots. This results in a red shift of the emission wavelength. In contrast, a higher growth temperature leads to a (here) even larger blue shift, caused by an increase of the As diffusion into the QDs. A higher growth temperature also increases dot size, but As and Sb intermixing is the dominating process causing the resulting (net) blue shift. With these growth parameters we could not achieve an emission wavelength beyond 1100 nm. To achieve emission around 1300 nm, two different approaches and parameter sets are used: On one hand a higher Sb/Ga ratio of 2/1 and a growth temperature of 561°C are chosen, because this way the red shift of the higher Sb/Ga ratio should exceed the blue shift resulting from the higher growth temperature. The PL measurement results are shown in the inset of Fig. 1a. An emission wavelength near the preferable value of 1300 nm is achieved, although PL intensity is still relatively low. The QDs have a density around 3·1010 cm-2 and a highly uniform size distribution (a diameter of 28±2 nm and a height of 4±1 nm). On the other hand the nominal coverage is reduced to 2 ML and an additional growth interruption of 10 s is scheduled after the deposition of the QDs. The other growth parameters are an Sb/Ga ratio of 1/1 and a growth temperature of 530°C. During the growth interruption the QDs are stabilized with an Sb flux. The PL spectrum is shown in Fig. 1b revealing an emission wavelength of 1225 nm. So far a disadvantage of both variations is a lower PL intensity resulting from a lower radiative recombination rate. By combining the new growth parameters with the growth interruption we are confident to achieve stronger PL signals and an emission wavelength closer to 1300 nm.