Structural And Optical Properties Of n-Type and p-Type GaAs(1−x)Bix Thin Films Grown By Molecular Beam Epitaxy On (311)B GaAs Substrates

In this paper, we report on the structural and optical properties of n-type Si-doped and p-type Be-doped GaAs(1−x)Bix thin films grown by molecular beam epitaxy on (311)B GaAs substrates with nominal Bi content x=5.4%. Similar samples without Bi were also grown for comparison purposes (n-type GaAs and p-type GaAs). X-ray diffraction, micro-Raman at room temperature, and photoluminescence (PL) measurements as a function of temperature and laser excitation power (PEXC) were performed to investigate their structural and optical properties. X-ray diffraction results revealed that the Bi incorporation in both n-type and p-type doped GaAsBi was similar, despite that the samples present remarkable differences in the number of Bi related defects, non-radiative centers and alloy disorder. Particularly, our results evidence that the Bi-related defects in n- and p-doped GaAsBi alloys have important impact on the differences of their optical properties

Effect of bismuth surfactant on the structural, morphological and optical properties of self-assembled InGaAs quantum dots grown by Molecular Beam Epitaxy on GaAs (001) substrates

In this work, we have investigated the effect of Bi surfactant on structural, morphological and optical properties of 5 monolayers self-assembled InGaAs quantum dots (QDs) grown on GaAs (001) substrates at various growth temperatures (435, 467 and 495 °C) by Molecular Beam Epitaxy. Two types of InGaAs QDs samples grown with and without exposure to bismuth were studied using Atomic Force Microscopy, Scanning Electron Microscopy, Transmission Electron Microscopy and Photoluminescence (PL). Our results have demonstrated that Bi-mediated growth provides improved control of several properties of InGaAs QDs including an enhancement of the QD PL peak intensity by 1.7 times as compared to InGaAs/GaAs control sample grown without Bi. In addition, a red-shift of the PL peak energy of about 40 meV was also observed when the InGaAs QDs were grown by using Bi evidencing that Bi surfactant affects considerably the size of QDs. Furthermore, the QDs grown with Bi surfactant exhibited a higher degree of size uniformity as demonstrated by the observation of narrower Full Width at Half Maximum (FWHM) of the PL peaks. We have also shown that both Bi surfactant and substrate temperature play an important role to control the density of InGaAs QDs. The QD density decreased from 8.9 × 1010 cm−2 (control sample) to 2.0 × 1010 cm−2 for the sample grown at the lowest temperature of 435 °C under Bi flux. All these approaches to control and improve the properties of self-assembled QDs are important for device applications that require high optical efficiency and low QD density