The development of an efficient group-IV light source that is compatible with the CMOS process remains a significant goal in Si-based photonics. Recently, the GeSn alloy has been identified as a promising candidate for realizing Si-based light sources. However, previous research suffered from a small wafer size, limiting the throughput and yield. To overcome this challenge, we report the successful growth of GeSn/Ge multiple-quantum-well (MQW) p-i-n LEDs on a 12-inch (300-mm) Si substrate. To the best of our knowledge, this represents the first report of semiconductor LEDs grown on such a large substrate. The MQW LED epitaxial layer is deposited on a 12-inch (300-mm) (001)-oriented intrinsic Si substrate using commercial reduced pressure chemical vapor deposition. To mitigate the detrimental effects of threading dislocation densities on luminescence, the GeSn/Ge is grown pseudomorphically. Owing to the high crystal quality and more directness in the bandgap, enhanced electroluminescence (EL) integrated intensity of 27.58 times is demonstrated compared to the Ge LED. The MQW LEDs exhibit EL emission near 2 μm over a wide operating temperature range of 300 to 450 K, indicating high-temperature stability. This work shows that GeSn/Ge MQW emitters are potential group-IV light sources for large-scale manufacturing.

Mechanical strain engineering has been promising for many integrated photonic applications. However, for the engineering of a material electronic bandgap, a trade-off exists between the strain uniformity and the integration compatibility with photonic-integrated circuits (PICs). Herein, we adopted a straightforward recess-type design of a silicon nitride (SiNx) stressor to achieve a uniform strain with enhanced magnitude in the material of interest on PICs. Normal-incidence, uniformly 0.56% tensile strained germanium (Ge)-on-insulator (GOI) metal-semiconductor-metal photodiodes were demonstrated, using the recessed stressor with 750 MPa tensile stress. The device exhibits a responsivity of 1.84±0.15A/W at 1550 nm. The extracted Ge absorption coefficient is enhanced by ～3.2× to 8340cm-1 at 1612 nm and is superior to that of In0.53Ga0.47As up to 1630 nm limited by the measurement spectrum. Compared with the nonrecess strained device, additional absorption coefficient improvement of 10%–20% in the C-band and 40%–60% in the L-band was observed. This work facilitates the recess-strained GOI photodiodes for free-space PIC applications and paves the way for various (e.g., Ge, GeSn or III-V based) uniformly strained photonic devices on PICs.

The heterogeneous integration of III–V devices with Si-CMOS on a common Si platform has shown great promise in the new generations of electrical and optical systems for novel applications, such as HEMT or LED with integrated control circuitry. For heterogeneous integration, direct wafer bonding (DWB) techniques can overcome the materials and thermal mismatch issues by directly bonding dissimilar materials systems and device structures together. In addition, DWB can perform at wafer-level, which eases the requirements for integration alignment and increases the scalability for volume production. In this paper, a brief review of the different bonding technologies is discussed. After that, three main DWB techniques of single-, double- and multi-bonding are presented with the demonstrations of various heterogeneous integration applications. Meanwhile, the integration challenges, such as micro-defects, surface roughness and bonding yield are discussed in detail.

High-performance GaInP/AlGaInP multi-quantum well light-emitting diodes (LEDs) grown on a low threading dislocation density (TDD) germanium-on-insulator (GOI) substrate have been demonstrated. The low TDD of the GOI substrate is realized through Ge epitaxial growth, wafer bonding, and layer transfer processes on 200 mm wafers. With O2 annealing, the TDD of the GOI substrate can be reduced to ～1.2×106 cm 2. LEDs fabricated on this GOI substrate exhibit record-high optical output power of 1.3 mW at a 670 nm peak wavelength under 280 mA current injection. This output power level is at least 2 times higher compared to other reports of similar devices on a silicon (Si) substrate without degrading the electrical performance. These results demonstrate great promise for the monolithic integration of visible-band optical sources with Si-based electronic circuitry and realization of high-density RGB (red, green, and blue) micro-LED arrays with control circuitry.

In this paper, normal incidence vertical p-i-n photodetectors on a germanium-on-insulator (GOI) platform were demonstrated. The vertical p-i-n structure was realized by ion-implanting boron and arsenic at the bottom and top of the Ge layer, respectively, during the GOI fabrication. Abrupt doping profiles were verified in the transferred high-quality Ge layer. The photodetectors exhibit a dark current density of ～47 mA/cm2 at ?1 V and an optical responsivity of 0.39 A/W at 1550 nm, which are improved compared with state-of-the-art demonstrated GOI photodetectors. An internal quantum efficiency of ～97% indicates excellent carrier collection efficiency of the device. The photodetectors with mesa diameter of 60 μm exhibit a 3 dB bandwidth of ～1 GHz, which agrees well with theoretical calculations. The bandwidth is expected to improve to ～32 GHz with mesa diameter of 10 μm. This work could be similarly extended to GOI platforms with other intermediate layers and potentially enrich the functional diversity of GOI for near-infrared sensing and communication integrated with Ge CMOS and mid-infrared photonics.