Fig. 1. Material characterization of multilayer MoS2 with and without Al2O3 stress liner. (a) Raman spectra of multilayer MoS2 sample grown on FS GaN substrate; the distance between E2g1 and A1g is 21.33  cm−2; (b) core level XPS spectrum of Mo 3d and S 2s of the control multilayer MoS2/GaN sample; (c) cross-sectional TEM image of the multilayer MoS2/GaN with 3 nm Al2O3; (d) Al, S, Mo, and Ca element fraction as a function of depth position. The position of Raman mode peaks for (e) E2g1 and (f) A1g of control and stress liner samples as a function of temperature including a linear fit.

Fig. 2. Simulation of multilayer MoS2 with tensile strain. (a) 2D stress mapping within the multilayer MoS2 (4 nm) photodetector with Al2O3 stress liner; (b) horizontal stress distribution within the multilayer MoS2 layer. Results of first-principles calculations: the variation of (c) the bottom of the conduction band and the top of the valence band, (d) bandgap, and (e) electron effective mass under different tensile strain on six-layer MoS2.

Fig. 3. Schematic and measurement of MoS2 photodetector with and without Al2O3 stress liner. (a) 3D schematic structure view of multilayer MoS2 photodetectors with the Al2O3 stress liner; (b) dark current and light current as a function of voltage under different power of the 365 nm incident light for control and stress liner photodetector; (c) extracted photocurrent of two photodetectors at 20 V with varying incident power. The straight lines were fitted by the power law (IPh∝Pα). (d) Calculated responsitivity of two photodetectors as a function of incident power.

Fig. 4. Performance of control and stress liner photodetectors. (a) Gain and EQE as a function of incident power; significant increases in both values for stress liner photodetector; (b) NEP and detectivity as a function of incident power; reduced performance of both for stress liner photodetector due to the increase in dark current.

Fig. 5. Time curve of photocurrent with a switch on/off light. (a) Photocurrent-time curve of control and stress liner photodetectors illuminated by 365 nm light source with the incident power of 5.647 μW at 20 V, respectively. The corresponding rise time (from 10% to 90% of maximum photocurrent) and the fall time (from 90% to 10% of maximum photocurrent) of (b) control and (c) stress liner photodetector, respectively.