Room temperature lasing from monolithically integrated gaas microdisks on Si

Additional functionalities on semiconductor microchips are progressively important in order to keep up with the ever increasing demand for more powerful computational systems. Recently, III-V integration on Si attracted significant research interest [1] due to the promise to merge mature Si CMOS processing technology with III-V semiconductors possessing superior material properties e.g. in terms of carrier mobility or band structure (direct band gap). In particular, Si photonics would strongly benefit from an integration scheme for active III-V optoelectronic devices in order to enable low-cost and power-efficient electronic-photonic integrated-circuits. In this regard, tremendous progress was achieved using various integration routes for laser sources including wafer bonding [2], buffer layers [3] or dislocation trapping [4].In this contribution, we report on room temperature lasing from GaAs microdisk cavities monolithically integrated on Si(001) using the template-assisted selective epitaxy (TASE) growth method [5]. First, the Si bulk substrate was thermally oxidized (ca. 130 nm) to facilitate efficient mode confinement. Afterwards the gain material is grown in 5x5 μm2, hollow SiO2 growth templates as sketched in Fig. 1a. SEM images indicate GaAs microdisks with a diameter of approx. 3.1 μm and height of 390 nm (c.f. bottom of Fig. 1a). These cavities were excited from the top using a pulsed (100 MHz with 15 ps pulse length) supercontinuum laser (NKT SuperK) and excitation wavelengths of 705 nm and 710 nm. Fig. 1b shows the power-dependent photoluminescence (PL) spectra measured at room temperature (the normalized spectra are displayed in the inset). For low excitations - up to a pulse energy of ca. 5 pJ - a broad emission peak is observed, thus, the emission is governed by spontaneous emission. Above 8 pJ per pulse a sharp peak (FWHM of 2.6 nm) around 880 nm appears on top of the spontaneous emission. The dramatic increase of this peak along with the threshold behaviour in linewidth indicates lasing threshold behaviour. The integrated intensity of this lasing peak increases by three orders of magnitude and the LL-curve (inset Fig. 1b) exhibits a typical S-shape. We determined a lasing threshold of approx. 15 pJ per pulse. Finally, the mode pattern observed using optical imaging (inset of Fig. 1b) resembles that of whispering gallery modes (WGMs). These results illustrate the potential of TASE regarding the integration of III-V semiconductors with high crystalline and optical quality on Si(001).