You are here: Home / UCL MBE group / Research Topic / InAs/GaAs QD Laser

InAs/GaAs QD Laser

Recently, Si-based photonic devices have attracted attention due to their ultra-fast optical data processing. However, Si has been seen as an inefficient light-emitting material because of its indirect band gap structure. Basing on the promised electronic and optical properties as well as the direct band gap structure of the III-V compounds, our recent research projects are focusing on the III-V quantum dot lasers monolithically grown on Si substrates.

There are several of the challenges associated with the direct epitaxial growth of III-V materials on Si substrate by molecular beam epitaxy (MBE), such as the antiphase boundaries (APBs) due to the polar/non-polar nature and the threading dislocation (TDs) due to the lattice mismatch between the III-V/Si. We use off-axis-cut substrate to solve the APBs and dislocation filter layers (DFLs) to reduce the TDs density. [1] According to our latest research, InAlAs/GaAs strained-layer superlattices (SLSs) serving as the DFLs offer a remarkable effect on preventing the propagations of TD into active region. [2] For the active region, we utilise III-V quantum dots (QDs) which offer the unique characteristics, in particular the high tolerance of temperature change, low threshold current density Jth, and insensitivity of the effect of detects comparing with the conventional quantum wells in building Si-based light-emitting devices.[3] Owing to the desired InAlAs/GaAs DFLs and high quality of QDs, the advanced achievements of the III-V quantum dot lasers based on the Si substrates have been obtained by our team.

Figure 1. (a) The schematic diagram of InAs/GaAs QD laser on Si (b) The L-I characteristics of QD laser with variable temperatures. The inset plot is the lasing spectrum of laser at 111 °C.

Figure 1a shows the structure of fabrication of our recent achievement of 1.3 mm InAs/GaAs QD Si-based laser, which can lase over a very wide range of temperatures with low injection current density and over 100 mW output power is achieved. [4] Figure 1b presents the plottings of L-I characteristics of QD laser with different temperatures. The maximum lasing temperature is 111°C, the detail lasing spectrum at that temperature has shown in insert plot of 1b where it lases at peak of ~1.29 mm. To the best of our knowledge this is the highest lasing temperature for InAs/GaAs QDs lasers directly grown on Si substrates right now. [4] Thus, our researches open up a new way to integrate Si-based laser with conventional III-V’s functionalities.

[1] Chen, R., Tran, T.-T., Ng, K.W., Ko, W.S., Chang, L.C., Sedgwick, F. G., and Chang-Hasnain, C.: ‘Nanolasers grown on silicon’, Nat. Photonics, 170–175 (2011)

[2] Tang, M., Chen, S., Wu, J., Jiang, Q., Dorogan, V.G., Benamara, M., Mazur, Y.I., Salamo, G.J., Seeds, A. and Liu, H., “1.3-μm InAs/GaAs quantum-dot lasers monolithically grown on Si substrates using InAlAs/GaAs dislocation filter layers,” Opt. Express, 22, 11528–11535 (2014).

[3] Liu, H., Li, H., Wu, J. and Wang, Z. M., “III–V Quantum-Dot Materials and Devices Monolithically Grown on Si Substrates,” in Silicon-based Nanomaterials, eds. Springer New York, 357–380 (2013).

[4] Chen, S.M., Tang, M.C., Wu, J., Jiang, Q., Dorogan, V.G., Benamara, M., Mazur, Y.I., Salamo, G.J., Seeds, A.J., and Liu, H., “1.3 μm InAs/GaAs quantum-dot laser monolithically grown on Si substrates operating over 100°C,” Electronics letters, vol. 50, No. 20, pp.1467-1468 (2014).