M. Reine, A. Hairston, P. Lamarre, K. Wong, S. Tobin, A. Sood, C. Cooke, M. Pophristic, S. Guo, B. Perez, R. Singh, C. Eddy, U. Chowdhury, M. Wong, R. Dupuis, T. Li, S. DenBaars
This paper reports the development of aluminum-gallium nitride (AlGaN or AlxGa1-xN) photodiode technology for high-operability 256×256 hybrid Focal Plane Arrays (FPAs) for solar-blind ultraviolet (UV) detection in the 260-280 nm spectral region. These hybrid UV FPAs consist of a 256×256 back-illuminated AlGaN p-i-n photodiode array, operating at zero bias voltage, bump-mounted to a matching 256×256 silicon CMOS readout integrated circuit (ROIC) chip. The unit cell size is 30×30 μm2. The photodiode arrays were fabricated from multilayer AlGaN films grown by MOCVD on 2" dia. UV-transparent sapphire substrates. Improvements in AlGaN material growth and device design enabled high quantum efficiency and extremely low leakage current to be achieved in high-operability 256×256 p-i-n photodiode arrays with cuton and cutoff wavelengths of 260 and 280 nm, placing the response in the solar-blind wavelength region (less than about 280 nm) where solar radiation is heavily absorbed by the ozone layer. External quantum efficiencies (at V=0, 270 nm, no antireflection coating) as high as 58% were measured in back-illuminated devices. A number of 256×256 FPAs, with the AlGaN arrays fabricated from films grown at three different facilities, achieved response operabilities as high as 99.8%, response nonuniformities (σ/μ) as low as 2.5%, and zero-bias resistance median values as high as 1×1016 ohm, corresponding to R0A products of 7×1010 ohm-cm2. Noise Equivalent Irradiance (NEI) data were measured on these FPAs. Median NEI values at 1 Hz are 250-500 photons/pixel-s, with best-element values as low as 90 photons/pixel-s at 1 Hz.
M. Reine, A. Hairston, P. Lamarre, K. Wong, S. Tobin, A. Sood, C. Cooke, M. Pophristic, S. Guo, B. Peres, R. Singh, C. Eddy, U. Chowdhury, M. Wong, R. Dupuis, T. Li, S. DenBaars
This paper reports the development of aluminum-gallium nitride (AlGaN or AlxGa1-xN) photodiode technology for high-operability 256×256 hybrid Focal Plane Arrays (FPAs) for solar-blind ultraviolet (UV) detection in the 260-280 nm spectral region. These hybrid UV FPAs consist of a 256×256 back-illuminated AlGaN p-i-n photodiode array, operating at zero bias voltage, bump-mounted to a matching 256×256 silicon CMOS readout integrated circuit (ROIC) chip. The unit cell size is 30×30 μm2. The photodiode arrays were fabricated from multilayer AlGaN films grown by MOCVD on 2" dia. UV-transparent sapphire substrates. Improvements in AlGaN material growth and device design enabled high quantum efficiency and extremely low leakage current to be achieved in high-operability 256×256 p-i-n photodiode arrays with cuton and cutoff wavelengths of 260 and 280 nm, placing the response in the solar-blind wavelength region (less than about 280 nm) where solar radiation is heavily absorbed by the ozone layer.
External quantum efficiencies (at V=0, 270 nm, no antireflection coating) as high as 58% were measured in backilluminated devices. A number of 256×256 FPAs, with the AlGaN arrays fabricated from films grown at three different facilities, achieved response operabilities as high as 99.8%, response nonuniformities (σ/μ) as low as 2.5%, and zero-bias resistance median values as high as 1×1016 ohm, corresponding to R0A products of 7×1010 ohm-cm2. Noise Equivalent Irradiance (NEI) data were measured on these FPAs. Median NEI values at 1 Hz are 250-500 photons/pixel-s, with best-element values as low as 90 photons/pixel-s at 1 Hz.
Properties of InGaN/AlInGaN/AlGaN single- and multiple-quantum-well (MQW) light-emitting diodes grown by MOCVD on sapphire substrates are investigated over a wide temperature range from 12 to 298 K. The room-temperature (RT) UV emission band, observed in both single-quantum-well (SQW) and MQW samples, is at 3.307 eV (375 nm) and its full width at half maximum is ~82 meV. In addition to the UV band, a blue emission band at 2.96 eV (419 nm) is observed in SQW samples. The relative intensities of these UV and blue emission bands depend on the injection current. We attribute the blue emission to the carrier overflow over the quantum well (QW) and subsequent radiative recombination involving a Mg-related-level in p-GaN. In MQW LEDs, we observe an anomalous temperature-induced "blue jump" between 170-190 K, with the main emission peak switching from blue to UV. The blue band emission dominates below 170 K, and is practically absent at RT. Thus, we demonstrate a significant advantage in utilizing MQW structures that provide a more effective capture of injected carriers into the QWs.
The requirements for maximizing the external quantum efficiency of UV nitride LEDs are discussed. It is shown that as the chip wavelength progressively decreases, nitride epi growth on a sapphire substrate becomes advantageous in terms of light extraction. The epilayer requirements for UV LEDs dictate the growth of n-AlGaN, with increasing Al contents, and the growth of UV-transparent p-GaN. It is shown that MOCVD growth in a Emcore D-180 or Ganzilla reactor is ideal for meeting the stringent epilayer requirements. Increasing light extraction efficiency and wall-plug efficiency also requires optimization of the reflecting P-contact. The relative merits of Al- and Ag-based reflecting contacts are discussed. Performance data for UV LEDs on sapphire, for drive currents up to 700 mA is shown. Finally, a practical high power UV-based white lamp is demonstrated.
High quality InAlGaN alloys, quantum wells and associated light emitting diodes have been grown by metalorganic chemical vapor deposition for ultraviolet (UV) emitters. In-situ reflection and ex-situ atomic force microscopy measurements show that InAlGaN epilayers and structures have good surface morphology. InAlGaN epilayers have also a narrow (0006) reflection X-ray diffraction rocking curve linewidth of ~ 340 arcsec and a strong band edge photoluminescence (PL) emission peak from 320 nm to 355 nm at room temperature. Several X-ray satellite peaks were observed from InAlGaN based quantum well structures, revealing that they were periodic with good interfaces. PL mapping measurements of the quantum well structures show excellent wavelength uniformity over a 2" wafer with a standard deviation of ~ 0.4% for structures emitting from 351-372 nm. Ultraviolet light emitting diodes (UV LEDs) based on the same InAlGaN quantum well structures have an electroluminescence (EL) emission at ~ 375 nm with a linewidth of ~10 nm and an excellent wavelength uniformity of less than 1 nm across a 2" wafer. Temperature dependent study of EL spectrum from an UV LED shows "blue jump" from a broad blue emission at <170 K to a narrow UV emission at higher temperatures.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.