GaN MSM photodetectors fabricated on bulk GaN with low dark‐current and high UV/visible rejection ratio

Won

et al. 2017

Sensors

The UV-to-visible rejection ratio is one of the important figure of merits of GaN-based UV photodetectors. For cost-effectiveness and large-scale fabrication of GaN devices, we tried to grow a GaN epitaxial layer on silicon substrate with complicated buffer layers for a stress-release. It is known that the structure of the buffer layers affects the performance of devices fabricated on the GaN epitaxial layers. In this study, we show that the design of a buffer layer structure can make effect on the UV-to-visible rejection ratio of GaN UV photodetectors. The GaN photodetector fabricated on GaN-on-silicon substrate with a step-graded AlxGa−xN buffer layer has a highly-selective photoresponse at 365-nm wavelength. The UV-to-visible rejection ratio of the GaN UV photodetector with the step-graded AlxGa1−xN buffer layer was an order-of-magnitude higher than that of a photodetector with a conventional GaN/AlN multi buffer layer. The maximum photoresponsivity was as high as 5 × 10−2 A/W. This result implies that the design of buffer layer is important for photoresponse characteristics of GaN UV photodetectors as well as the crystal quality of the GaN epitaxial layers.

Section: Resultssupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Selectively Enhanced UV-A Photoresponsivity of a GaN MSM UV Photodetector with a Step-Graded AlxGa1−xN Buffer Layer

Won

et al. 2017

Sensors

“…The average UV-to-visible rejection ratio was about 10 2 for any bias condition. This value is slightly lower than that of the values previously reported in the literatures [ 7 , 8 , 9 ]. The maximum value of the UV-to-visible rejection ratio was 10 3 at 1 V bias calculated by the ratio of responsivity values at 365-nm and 450-nm wavelengths.…”

Section: Resultscontrasting

confidence: 66%

“…To fabricate the UV photodetector, GaN is one of proper materials because it has a wide bandgap of 3.4 eV corresponding to the UV wavelength region. In the last two decades, various types of GaN-based UV photodetectors or other material-based UV photodetectors were proposed and reported in literatures [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. The metal-semiconductor-metal (MSM)-type UV photodetector is the most appropriate device for a development of an optoelectronic integrated circuit compared to those of other-type photodetectors because of its simple fabrication process, low dark current density, and high process compatibility.…”

Section: Introductionmentioning

confidence: 99%

GaN-Based Ultraviolet Passive Pixel Sensor on Silicon (111) Substrate

Won

et al. 2019

Sensors

The fabrication of a single pixel sensor, which is a fundamental element device for the fabrication of an array-type pixel sensor, requires an integration technique of a photodetector and transistor on a wafer. In conventional GaN-based ultraviolet (UV) imaging devices, a hybrid-type integration process is typically utilized, which involves a backside substrate etching and a wafer-to-wafer bonding process. In this work, we developed a GaN-based UV passive pixel sensor (PPS) by integrating a GaN metal-semiconductor-metal (MSM) UV photodetector and a Schottky-barrier (SB) metal-oxide-semiconductor field-effect transistor (MOSFET) on an epitaxially grown GaN layer on silicon substrate. An MSM-type UV sensor had a low dark current density of 3.3 × 10−7 A/cm2 and a high UV/visible rejection ratio of 103. The GaN SB-MOSFET showed a normally-off operation and exhibited a maximum drain current of 0.5 mA/mm and a maximum transconductance of 30 μS/mm with a threshold voltage of 4.5 V. The UV PPS showed good UV response and a high dark-to-photo contrast ratio of 103 under irradiation of 365-nm UV. This integration technique will provide one possible way for a monolithic integration of the GaN-based optoelectronic devices.

Physica Rapid Research Ltrs

“…Among these, GaN is a promising candidate for UV detector applications due to its direct bandgap and high saturation velocity, which offers high photoresponse and fast transient characteristics. Over the past few years, various types of GaN‐based PDs, such as p–n junction, p‐i‐n diodes, Schottky barrier, and metal–semiconductor–metal (MSM) PDs, have been proposed. Among them, MSM PDs are preferred due to their easy integration with field‐effect‐transistor (FET)‐based electronics and relatively fast response, which is a key figure of merit for PDs.…”

Section: A Summary Of Schottky Junction Parameters Estimated Using Thmentioning

confidence: 99%

Role of ZrO₂ Passivation Layer Thickness in the Fabrication of High‐Responsivity GaN Ultraviolet Photodetectors

Chatterjee

Khamari

Porwal

et al. 2019

The importance of a ZrO2 passivation layer in the fabrication of high‐responsivity GaN‐based ultraviolet (UV) photodetectors (PDs) is discussed. It is found that an optimum thickness of the ZrO2 layer exists, which plays a critical role in controlling the photoresponse and transient response of the device. Beyond the optimal thickness, the performance of PDs deteriorates, which is limited by the restricted tunneling of photogenerated carriers across the oxide layer. At an optimum ZrO2 thickness of 3 nm, a spectral responsivity of 27 A W−1 at 361 nm is achieved at 4 V applied bias along with the fast response of the device with a rise (fall) time of 28 ms (178 ms), respectively. Such characteristics are found to be similar or better than the recently reported state‐of‐the‐art values for visible blind metal–semiconductor–metal PDs fabricated on GaN. The results confirm that the surface passivation with an optimal thickness of an oxide layer can be used to develop high‐responsivity GaN‐based UV PDs irrespective of having a large dark current, which is often inevitable due to the presence of a large density of dislocations in GaN epitaxial layers grown on foreign substrates.