Enhanced GeSn Microdisk Lasers Directly Released on Si

Abstract

complementarymetal-oxide-semiconductor (CMOS) processing limits the practical realization of these long-sought-after PICs. [2] Germanium (Ge) has been extensively explored for such a laser owing to its CMOS compatibility and near-direct bandgap configuration. [3,4] Among various approaches to achieve the bandgap directness, strain engineering [5][6][7][8][9][10][11][12][13] and tin (Sn) alloying [14][15][16][17] have been considered as the two most promising paradigms.While lasing action has been observed in strain-engineered Ge at low operating temperatures (<100 K), [18][19][20] the Sn alloying approach has made significant, steady progress toward achieving lasing at practically high temperature over the past few years. [21][22][23][24][25][26][27] Since the first lasing demonstration in GeSn at 90 K, [21] much effort has been focused on increasing the operating temperature. [21][22][23][24][25][26][27] A major route to this end has been to increase the Sn content to further increase the directness of GeSn alloys, [17] which enabled higher operating temperatures reaching 270 K. [27] However, the lasing thresholds at these elevated temperatures are very high (>800 kW cm −2 at 270 K). [27] The exact causes for such high threshold in direct bandgap GeSn lasers have been attributed to the material quality. [17] For instance, it has been suggested that a large content of Sn increases the nonradiative recombination rate, thus leading to the reduction of internal quantum efficiency which influences the lasing threshold significantly. [17] In addition, the Sn alloying is typically accompanied by the compressive strain in the GeSn layer due to the large lattice mismatch between GeSn and Ge buffer layers. [15] Such compressive strain reduces the directness of GeSn, [28,29] thereby hindering the lasing performance. [30] Additionally, the increase in Sn content requires a decrease in growth temperature, which is typically associated with a higher concentration of point defects (vacancies and vacancies complexes) that can also impact the laser performance due to carrier trapping. [31,32] Another route to improve the lasing performance is to simultaneously employ both strain engineering and Sn alloying. [28,33] Recently, a few research groups have made significant progress along this direction by relaxing the compressive strain [22,34] and also by inducing mechanical tensile strain in GeSn. [35,36] Despite the improved directness of strain-engineered GeSn over as-grown compressively strained GeSn, the suspended device configuration, which has thus far been necessary for GeSn alloys are promising candidates for complementary metal-oxidesemiconductor-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 ...

High carrier lifetimes in epitaxial germanium–tin/Al(In)As heterostructures with variable tin compositions

“…Adding B8% Sn to Ge, compensates the 0.13 eV difference between the Ge Gand L-valleys due to a more rapid decrease in the conduction band minimum of the former, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] similar to B1.6% tensile strain in epitaxial Ge. [19][20][21] The Ge 1Ày Sn y material system offers (i) a tunable Ge 1Ày Sn y bandgap by varying Sn incorporation while simultaneously maintaining lattice-matching with an underlying virtual substrate, e.g., In x Al 1Àx As; (ii) a carrier confinement within Ge 1Ày Sn y for electronic (i.e., electronic transport only through the GeSn material when it has been deposited on a large bandgap buffer, such as In x Al 1Àx As) and photonic (i.e., the different refractive indices of Ge 1Ày Sn y and In x Al 1Àx As) applications; (iii) potential as a source material in Ge 1Ày Sn y / In x Ga 1Àx As and similar heterojunction-based, ultra-low voltage tunnel transistors; [22][23][24][25][26] (iv) high responsivity when used as a photodetector material; 1,[27][28][29][30][31] (v) compatibility with Si CMOS technology; 32-38 and (vi) an increased mobility due to a lower effective mass (m eff ) (high ON current, and therefore the opportunity for circuit-level scaling at low voltages). In light of the aforementioned advantages, researchers have been aggressively investigating epitaxial Ge 1Ày Sn y on Si and Ge/Si [1][2][3][4]…”

“…, electronic transport only through the GeSn material when it has been deposited on a large bandgap buffer, such as In x Al 1− x As) and photonic ( i.e. , the different refractive indices of Ge 1− y Sn y and In x Al 1− x As) applications; (iii) potential as a source material in Ge 1− y Sn y /In x Ga 1− x As and similar heterojunction-based, ultra-low voltage tunnel transistors; 22–26 (iv) high responsivity when used as a photodetector material; 1,27–31 (v) compatibility with Si CMOS technology; 32–38 and (vi) an increased mobility due to a lower effective mass ( m eff ) (high ON current, and therefore the opportunity for circuit-level scaling at low voltages). In light of the aforementioned advantages, researchers have been aggressively investigating epitaxial Ge 1− y Sn y on Si and Ge/Si 1–18 and Ge 1− y Sn y on amorphous materials for the development of the next generation of photodetectors and lasers.…”

Second-harmonic generation in germanium-on-insulator from visible to telecom wavelengths

“…In contrast, for Ge, there is only a theoretical prediction of the mid-infrared (MIR) SHG in a strained Ge waveguide 16 . Since Ge is already on the list of materials in the Si photonics foundry and has recently gained prominence for on-chip lasers [17][18][19][20][21][22] and MIR waveguides 23,24 . It is desirable to enable and enhance second-order nonlinear optical processes in Ge to widen the functionality of this important material.…”

Impact of strain engineering and Sn content on GeSn heterostructured nanomaterials for nanoelectronics and photonic devices

“…Youngmin Kim et al prepared a p-i-n heterostructure of 3 GeSn layers with 5-7-5% Sn content deposited on 130 and 200 nm buffer GeSn layers on Ge above the Si substrate, then the Ge buffer was selectively etched so that 11 mm diameter microdisk was directly stacked on Si. A 2215 nm lasing line was detected at 4 K with a pumping threshold power equal to 60 kW cm À2 139. Bibin Wang et al deposited 500 nm-thick GeSn with 10.5% Sn content on the SiN stressor layer above the Al heat sink layer.…”