Low temperature photoconductivity of few layer p-type tungsten diselenide (WSe2) field-effect transistors (FETs)

We report on the low-temperature photoconductive properties of few layer p-type tungsten diselenide (WSe2) field-effect transistors (FhTs) synthesized using the chemical vapor transport method. Photoconductivity measurements show that these FhTs display room temperature photo-responsivities of similar to 7 mAW(-1) when illuminated with a laser of wavelength lambda = 658 nm with a power of 38 nW. The photo-responsivities of these FhTs showed orders of magnitude improvement (up to similar to 1.1 AW(-1) with external quantum efficiencies reaching as high as similar to 188%) upon application of a gate voltage (V-G = -60 V). A temperature dependent (100 K < T < 300 K) photoconductivity study reveals a weak temperature dependence of responsivity for these WSe2 phototransistors. We demonstrate that it is possible to obtain stable photo-responsivities of similar to 0.76 +/- 0.2 AW(-1 )(with applied V-G = -60 V), at low temperatures in these FhTs. These findings indicate the possibility of developing WSe2-based FETs for highly robust, efficient, and swift photodetectors with a potential for optoelectronic applications over a broad range of temperatures.