Effects of Annealing on the Behavior of Sn in GeSn Alloy and GeSn-Based Photodetectors

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

“…Alloying tin (Sn) with epitaxial germanium (Ge) (i.e., Ge 1Ày Sn y ) during material synthesis offers several advantages, chief among them being that the bandgap of Ge will be converted from an indirect (a conduction band minimum located at L-valley) bandgap to a direct bandgap (a conduction band minimum at G-valley) material, which can enhance absorption and improve the photodetector response. 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).…”

Review of Si-Based GeSn CVD Growth and Optoelectronic Applications

“…[ 33 , 34 , 35 , 36 , 37 ]. Growing high-quality GeSn layers with relatively high Sn contents has different challenges, e.g., Sn segregation during growth and the poor thermal stability of SnGe layers [ 38 , 39 , 40 , 41 ]. These issues root from the low solid solubility of Sn in Ge (<1%) and the large lattice mismatch between Si or Ge and GeSn.…”

Flexible Titanium Nitride/Germanium-Tin Photodetectors Based on Sub-Bandgap Absorption

“…The responsivity of flat TiN/GeSn PDs was further enhanced to 148.5 mA W –1 , corresponding to an EQE of 13% at 1550 nm. The responsivity is comparable to or higher than those of GeSn PDs. ,− Another significant enhancement is the ∼180 nm extension of absorption coverage wavelength as indicated in arrows of Figure c, leading to the shift of the cutoff wavelength to a longer wavelength. As shown in Figure d, the detectivity of flat TiN/GeSn PDs at 1550 nm was calculated to be 8 × 10 8 cm Hz –1 W –1 , which is eight times higher than that of flat GeSn PDs.…”