남동욱 교수

This work presents a novel method to introduce a sustainable biaxial tensile strain larger than 1% in a thin Ge membrane using a stressor layer integrated on a Si substrate. Raman spectroscopy confirms 1.13% strain and photoluminescence shows a direct band gap reduction of 100meV with enhanced light emission efficiency. Simulation results predict that a combination of 1.1% strain and heavy n(+) doping reduces the required injected carrier density for population inversion by over a factor of 60.

Semiconductor heterostructures play a vital role in photonics and electronics. They are typically realized by growing layers of different materials, complicating fabrication and limiting the number of unique heterojunctions on a wafer. In this Letter, we present single-material nanowires which behave exactly like traditional heterostructures. These pseudoheterostructures have electronic band profiles that are custom-designed at the nanoscale by strain engineering. Since the band profile depends

In this paper, we present a comprehensive study of carrier statistics in germanium with high uniaxial strain along the [100] direction. Several types of PL experiments were conducted to investigate polarization-, temperature- and excitation-dependent carrier statistics in germanium under various amounts of uniaxial strain. With the ability to clearly resolve multiple photoluminescence peaks originating from strain-induced valence band splitting, we experimentally observed strongly polarized ligh

Abstract GeSn alloys are promising candidates for complementary metal‐oxide‐semiconductor‐compatible, tunable lasers. Relaxation of residual compressive strain in epitaxial GeSn has recently shown promise in improving the lasing performance. However, the suspended device configuration that is thus far introduced to relax the strain is destined to limit heat dissipation, thus hindering the device performance. Herein is demonstrated that strain‐free GeSn microdisk laser devices fully released on S

We report improved minority carrier lifetimes in n-type-doped and tensile-strained germanium by measuring direct bandgap photoluminescence from germanium-on-insulator substrates with various levels of defect density. We first describe a method to fabricate a high-quality germanium-on-insulator substrate by employing direct wafer bonding and chemical-mechanical polishing. Raman spectroscopy measurement was performed to assess the purity of the transferred layer on an insulator. Using time-resolve

Two-dimensional (2D) materials-based photodetectors in the infrared range hold the key to enabling a wide range of optoelectronics applications including infrared imaging and optical communications. While there exist 2D materials with a narrow bandgap sensitive to infrared photons, a two-photon absorption (TPA) process can also enable infrared photodetection in well-established 2D materials with large bandgaps such as WSe₂ and MoS₂. However, most of the TPA photodetectors s

Strained germanium nanowires have recently become an important material of choice for silicon-compatible optoelectronic devices. While the indirect bandgap nature of germanium had long been problematic both in light absorption and emission, recent successful demonstrations of bandstructure engineering by elastic strain have opened up the possibility of achieving direct bandgap in germanium, paving the way towards the realization of various high-performance optical devices integrated on a silicon

GeSn alloys offer a promising route towards a CMOS compatible light source and the realization of electronic-photonic integrated circuits. One tactic to improve the lasing performance of GeSn lasers is to use a high Sn content, which improves the directness. Another popular approach is to use a low to moderate Sn content with either compressive strain relaxation or tensile strain engineering, but these strain engineering techniques generally require optical cavities to be suspended in air, which

Complementary metal oxide semiconductor-compatible short- and midwave infrared emitters are highly coveted for the monolithic integration of silicon-based photonic and electronic integrated circuits to serve a myriad of applications in sensing and communication. In this regard, the group IV germanium–tin (GeSn) material epitaxially grown on silicon (Si) emerges as a promising platform to implement tunable infrared light emitters. Indeed, upon increasing the Sn content, the bandgap of GeSn narrow

We present germanium microdisk optical resonators under a large biaxial tensile strain using a CMOS-compatible fabrication process. Biaxial tensile strain of ~0.7% is achieved by means of a stress concentration technique that allows the strain level to be customized by carefully selecting certain lithographic dimensions. The partial strain relaxation at the edges of a patterned germanium microdisk is compensated by depositing compressively stressed silicon nitride layer. Two-dimensional Raman sp

Graphene-based optoelectronic devices have recently attracted much attention for the next-generation electronic-photonic integrated circuits. However, it remains elusive whether it is feasible to create graphene-based lasers at the chip scale, hindering the realization of such a disruptive technology. In this work, we theoretically propose that Landau-quantized graphene enabled by strain-induced pseudomagnetic field can become an excellent gain medium that supports lasing action without requirin

Single-photon emitters (SPEs) hold the key to many quantum technologies including quantum computing. In particular, developing a scalable array of identical SPEs can play an important role in preparing single photons - crucial resources for computation - at a high rate, allowing to improve the computational capacity. Recently, different types of SPEs have been found in various 2D materials. Towards realizing scalable SPE arrays in 2D materials for quantum computation, it is required to develop t

GeSn alloys are a promising emerging complementary metal–oxide–semiconductor compatible technology for applications in photonics and electronics. However, the unavoidable intrinsic compressive strain introduced during epitaxial growth has prevented researchers from pushing the performance of GeSn devices to the limit and realizing real-world applications. In this paper, we present a straightforward geometric strain-inversion technique that harnesses the harmful compressive strain to achieve bene

Two-dimensional (2D) materials have emerged as promising candidates for next-generation integrated single-photon emitters (SPEs). However, significant variability in the emission energies presents a major challenge in producing identical single photons from different 2D SPEs, which may become crucial for practical quantum applications. Although various approaches to dynamically tuning the emission energies of 2D SPEs have been developed to address the issue, the practical solution to matching mu