Abstract
Deep ultra-violet semiconductor lasers have numerous applications for optical storage and biochemistry. Many strategies based on nitride heterostructures and adapted substrates have been investigated to develop efficient active layers in this spectral range, starting with AlGaN quantum wells on AlN substrates and more recently sapphire and SiC substrates. Here we report an efficient and simple solution relying on binary GaN/AlN quantum wells grown on a thin AlN buffer layer on a silicon substrate. This active region is embedded in microdisk photonic resonators of high quality factors and allows the demonstration of a deep ultra-violet microlaser operating at 275 nm at room temperature under optical pumping, with a spontaneous emission coupling factor β = (4 ± 2) 10−4. The ability of the active layer to be released from the silicon substrate and to be grown on silicon-on-insulator substrates opens the way to future developments of nitride nanophotonic platforms on silicon.
Highlights
The structure is composed of an AlN disk with twenty GaN/AlN quantum wells (0.7 nm quantum well – 5 nm barrier), maintained by a silicon post on a silicon substrate; the distribution of the electric field intensity of a whispering gallery modes (WGMs) is illustrated on the top of the disk, as calculated for a TE mode in a 2 μ m-diameter microdisk
We demonstrate microdisk lasers on a silicon substrate operating in pulsed mode at room temperature in the UV-C spectral range
We show that this particular active layer leads to a narrow optical emission with a strong oscillator strength, with enough carrier confinement to maintain a large internal quantum efficiency at room temperature
Summary
The microdisk structures are fabricated with a dedicated process for nitride nanophotonics (Fig. 1)[19]. Its spectral width is only 50 meV FWHM, a fraction of the PL inhomogeneous broadening This can be understood as the frontier between the low energy part of the density of states, more sensitive to disorder, and higher energy states, that contribute the high spectral gain density of the present GaN/AlN QWs. the flexibility of the present nitride-on-silicon approach is demonstrated with a variant of the microlaser directly lying on oxide instead of forming a free-standing disk with a silicon post. We demonstrate the first microlaser emitting in the deep UV range below 300 nm and at room temperature It is based on the combination of a high quality microdisk resonator and a simple active layer based on thin binary GaN/AlN QWs grown on Si or SOI substrates. The combination of these three features opens the way to short wavelength integrated sources for UV photonics on silicon and SOI substrates
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