Abstract
GeSn is an attractive semiconductor material for Si-based photonics. However, large lattice mismatch between GeSn and Si and the low solubility of Sn in Ge limit its development. In order to obtain high Sn-content GeSn on Si, it is normally grown at low temperature, which would lead to inevitable dislocations. Here, we reported a single-crystal defect-free graded GeSn on insulator (GSOI) stripes laterally grown by rapid melting growth (RMG). The Sn-content reaches to 14.2% at the end of the GSOI stripe. Transmission electron microscopy observation shows the GSOI stripe without stacking fault and dislocations. P-channel pseudo metal-oxide-semiconductor field effect transistors (MOSFETs) and metal-semiconductor-metal (MSM) Schottky junction photodetectors were fabricated on these GSOIs. Good transistor performance with a low field peak hole mobility of 402 cm2/Vs is obtained, which indicates a high-quality of this GSOI structure. Strong near-infrared and short-wave infrared optical absorption of the MSM photodetectors at 1550 nm and 2000 nm were observed. Owing to high Sn-content and defect-free, responsivity of 236 mA/W@-1.5 V is achieved at 1550 nm wavelength. In addition, responsivity reaches 154 mA/W@-1.5 V at 2000 nm with the optical absorption layer only 200 nm-thick, which is the highest value reported for GeSn junction photodetectors until now.
Highlights
GeSn is an attractive semiconductor for Si-based photonics due to its special energy band structure and the compatibility with complementary metal oxide semiconductor (CMOS) processes[1,2,3,4,5,6,7,8]
rapid melting growth (RMG) is a potential technique in growing defect-free and tensile strained GeSn on insulator (GSOI) stripes with high Sn-content
The gradient of Sn-content was created along the GSOI by growing process, which was in agreement with calculated results based on Scheil equation
Summary
GeSn is an attractive semiconductor for Si-based photonics due to its special energy band structure and the compatibility with complementary metal oxide semiconductor (CMOS) processes[1,2,3,4,5,6,7,8]. Compressive strain increases the energy difference between Γ valley and L valley in conduction band of GeSn, and offsets the bandgap shrink induced by Sn incorporation, which prevents direct bandgap transformation and high absorption coefficient[4,5,7,8,9] For these reasons, the key to enhance the optical absorption and light emission performance is promoting the Sn-content and crystal quality, and relaxing the compressive strain (even obtains tensile strain) of GeSn layer. It is a great challenge to grow strain relaxed, high-quality, and high Sn-content GeSn. Recently, a technique (RMG), similar to Czochralski crystal growth process, about fabricating defect-free Ge on insulator (GOI) has been described[19,20], in which single-crystal Si was used as a crystal seed for lateral liquid phase epitaxial growth. Responsivity reaches 154 mA/W@-1.5 V at 2000 nm with the optical absorption layer only 200 nm, which is the highest result reported for GeSn junction photodetectors until now
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