Superlinear composition-dependent photocurrent in CVD-grown monolayer MoS2(1-x)Se2x alloy devices.
Transition metal dichalcogenides (TMDs) have emerged as a new class of two-dimensional materials that are promising for electronics and photonics. To date, optoelectronic measurements in these materials have shown the conventional behavior expected from photoconductors such as a linear or sublinear dependence of the photocurrent on light intensity. Here, we report the observation of a new regime of operation where the photocurrent depends superlinearly on light intensity. We use spatially resolved photocurrent measurements on devices consisting of CVD-grown monolayers of TMD alloys spanning MoS2 to MoSe2 to show the photoconductive nature of the photoresponse, with the photocurrent dominated by recombination and field-induced carrier separation in the channel. Time-dependent photoconductivity measurements show the presence of persistent photoconductivity for the S-rich alloys, while photocurrent measurements at fixed wavelength for devices of different alloy compositions show a systematic decrease of the responsivity with increasing Se content associated with increased linearity of the current-voltage characteristics. A model based on the presence of different types of recombination centers is presented to explain the origin of the superlinear dependence on light intensity, which emerges when the nonequilibrium occupancy of initially empty fast recombination centers becomes comparable to that of slow recombination centers.
Velveth
V
Klee
Edwin
E
Preciado
David
D
Barroso
Ariana E
AE
Nguyen
Chris
C
Lee
‡Sandia National Laboratories, Livermore, California 94551, United States.
Kristopher J
KJ
Erickson
‡Sandia National Laboratories, Livermore, California 94551, United States.
Mark
M
Triplett
Brandon
B
Davis
I-Hsi
IH
Lu
Sarah
S
Bobek
Jessica
J
McKinley
Joseph P
JP
Martinez
John
J
Mann
‡Sandia National Laboratories, Livermore, California 94551, United States.
A Alec
AA
Talin
Ludwig
L
Bartels
‡Sandia National Laboratories, Livermore, California 94551, United States.
François
F
Léonard
D000497:Alloys / Q000737:chemistry / Q000528:radiation effects; D003460:Crystallization / Q000379:methods; D004220:Disulfides / Q000737:chemistry* / Q000528:radiation effects*; D004553:Electric Conductivity; D004563:Electrochemistry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005740:Gases / Q000737:chemistry; D008027:Light; D016014:Linear Models; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000528:radiation effects*; D008956:Models, Chemical; D008982:Molybdenum / Q000737:chemistry* / Q000528:radiation effects*; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods; D010777:Photochemistry / Q000295:instrumentation*; D011829:Radiation Dosage
D000497:Alloys; D004220:Disulfides; D005740:Gases; D008982:Molybdenum; C082964:molybdenum disulfide
MoS2; MoSe2; Transition metal dichalcogenides; alloys; photocurrent; superlinear