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Atomically thin 2D transition metal dichalcogenides (TMDs), such as MoS2, are promising candidates for nanoscale photonics because of strong light–matter interactions. However, Fermi‐level pinning due to metal‐induced gap states (MIGS) at the metal–monolayer (1L)‐MoS2interface limits the application of optoelectronic devices based on conventional metals due to high contact resistance. On the other hand, a semimetal–TMD–semimetal device can overcome this limitation, where the MIGS are sufficiently suppressed allowing ohmic contacts. Herein, the optoelectronic performance of a bismuth–1L‐MoS2–bismuth device with ohmic electrical contacts and extraordinary optoelectronic properties is demonstrated. To address the wafer‐scale production, full coverage 1L‐MoS2grown by chemical vapor deposition. High photoresponsivity of 300 A W−1at wavelength 400 nm measured at 77 K, which translates into an external quantum efficiency (EQE) ≈1000 or 105%, is measured. The 90% rise time of the devices at 77 K is 0.1 ms, suggesting they can operate at the speed of ≈10 kHz. High‐performance broadband photodetector with spectral coverage ranging from 380 to 1000 nm is demonstrated. The combination of large‐array device fabrication, high sensitivity, and high‐speed response offers great potential for applications in photonics, including integrated optoelectronic circuits.
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This abstract presents a study on the avalanche capability of GaN p-i-n diode leading to the achievement of 60A/W, 278V GaN avalanche photodiode. The GaN p-i-n diode fabricated on a free-standing GaN substrate was avalanche capable due to optimal edge termination. Both electrical and optical characterizations were conducted to validate the occurrence of avalanche in these devices. The device showed a positive temperature coefficient of breakdown voltage, which follows the nature of avalanche breakdown. The positive coefficient was measured to be 3.85 ×10^(-4) K^(-1) (0.1V/K) under a measurement temperature ranges from 300 K to 525 K. Moreover, the fabricated device showed excellent performance as an avalanche photo detector with record device metrics: (1) record high photoresponsivity of 60 A/W; (2) high optical gain of 10^5 ; and (3) low cark current. Robust avalanche is a key requirement in various device applications and necessary for their reliable operation.more » « less
