We review epitaxial formation, basic properties, and device applications of a novel type of nanostructures of mixed (0D/2D) dimensionality that we refer to as quantum well-dots (QWDs). QWDs are formed by metalorganic vapor phase epitaxial deposition of 4–16 monolayers of In_xGa_1−xAs of moderate indium composition (0.3 < x < 0.5) on GaAs substrates and represent dense arrays of carrier localizing indium-rich regions inside In-depleted residual quantum wells. QWDs are intermediate in properties between 2D quantum wells and 0D quantum dots and show some advantages of both of those. In particular, they offer high optical gain/absorption coefficients as well as reduced carrier diffusion in the plane of the active region. Edge-emitting QWD lasers demonstrate low internal loss of 0.7 cm⁻¹ and high internal quantum efficiency of 87%. as well as a reasonably high level of continuous wave (CW) power at room temperature. Due to the high optical gain and suppressed non-radiative recombination at processed sidewalls, QWDs are especially advantageous for microlasers. Thirty-one μm in diameter microdisk lasers show a high record for this type of devices output power of 18 mW. The CW lasing is observed up to 110 °C. A maximum 3-dB modulation bandwidth of 6.7 GHz is measured in the 23 μm in diameter microdisks operating uncooled without a heatsink. The open eye diagram is observed up to 12.5 Gbit/s, and error-free 10 Gbit/s data transmission at 30 °C without using an external optical amplifier, and temperature stabilization is demonstrated.

We study injection GaAs-based microdisk lasers capable of operating at room and elevated temperatures. A novel type of active region is used, namely InGaAs quantum well-dots representing a dense array of indium-rich islands formed inside an indium-depleted residual quantum well by metalorganic vapor phase epitaxy. We demonstrate a high output power of 18 mW, a differential efficiency of about 31%, and a peak electrical-to-optical power conversion efficiency of 15% in a 31 μm diameter microdisk laser. The continuous-wave lasing is observed up to 110°C.

We fabricated and tested a quantum well laser with asymmetric barrier layers. Such a laser has been proposed earlier to suppress bipolar carrier population in the optical confinement layer and thus to improve temperature-stability of the threshold current. As compared to the conventional reference laser structure, our laser with asymmetric barrier layers demonstrates reduced internal optical loss, lower threshold current density at elevated temperatures, and higher characteristic temperature (143 vs. 99 K at 20 °C).

We report on direct large signal modulation and the reliability studies of microdisk lasers based on InGaAs/GaAs quantum well-dots. A 23 μm in diameter microlaser exhibits an open eye diagram up to 12.5 Gbit/s and is capable of error-free 10 Gbit/s data transmission at 30°C without temperature stabilization. The ageing tests of a 31 μm in diameter microdisk laser were conducted at room and elevated temperatures during more than 1200 hr. The average rate of the output power degradation was about 25 and 29 nW/hr at 40°C and 60°C, respectively.

GaAs-based microdisk lasers with an active region representing a dense array of indium-rich islands (InGaAs quantum well-dots) were studied using direct small-signal modulation. We demonstrate that using dense arrays of InGaAs quantum well-dots enables uncooled high-frequency applications with a GHz-range bandwidth for microdisk lasers. A maximum 3 dB modulation frequency of 5.9 GHz was found in the microdisk with a radius of 13.5 μm operating without a heatsink for cooling. A modulation current efficiency factor of $1.5\mathrm{GHz}/{\mathrm{mA}}^{1/2}$ was estimated.

We present design, fabrication and characterization of an optically pumped MEMS VCSELwhich utilizes a silicon-on-insulator wafer for the microelectromechanical system and encapsulates the MEMS by direct InP wafer bonding, which improves the protection and control of the tuning element. This procedure enables a more robust fabrication, a larger free spectral range and facilitates bidirectional tuning of the MEMS element. The MEMS VCSEL device uses a high contrast grating mirror on a MEMS stage as the bottom mirror, a wafer bonded InP with quantum wells for amplification and a deposited dielectric DBR as the top mirror. A 40 nm tuning range and a mechanical resonance frequency in excess of 2 MHz are demonstrated.