200 nm deep ultraviolet photodetectors based on AlN

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AlN homoepilayers and heteroepilayers were grown on polar c-plane and nonpolar a-plane and m-plane orientations of AlN bulk and sapphire substrates by metal organic chemical vapor deposition. A systematic comparative study of photoluminescence properties of these samples revealed that all AlN homoepilayers ͑c, a and m planes͒ were strain free with an identical band gap of about 6.099 ͑6.035͒ eV at 10 ͑300͒ K, which is about 42 meV below the band gap of c-plane AlN heteroepilayers grown on sapphire. Also, nonpolar a-plane homoepilayers have the highest emission intensity over all other types of epilayers. We believe that a-plane AlN homoepilayers have the potential to provide orders of magnitude improvement in the performance of new generation deep UV photonic devices. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2965613͔ AlN has a complete solid solubility with GaN ͑Ref. 1͒ and emerged as an important semiconductor material for applications of light emitters down to 200 nm ͑Ref. 2͒ and detectors in the deep ultraviolet ͑DUV͒ and extreme UV spectral region. 3,4 Quantum wells ͑QWs͒ have been the device structure of choice for efficient III-nitride semiconductor based light emitters. 5,6 Conventional nitride c-plane multiple QW structures generate fixed sheet charges at the interfaces due to the spontaneous and piezoelectric polarization. 7-10 which induce internal electric fields, lead to carrier separation, and reduce the radiative recombination rate. Consequently, optoelectronic devices such as light emitting diodes and laser diodes based on heteroepitaxial c-plane oriented III-nitride materials possess reduced internal quantum efficiencies.There has been tremendous effort in the investigation of nonpolar a-plane and m-plane III-nitride epilayers 11 and optoelectronic devices with QW structures 9,10 to reduce the effects of internal electric fields. To achieve QW and other heterostructure based devices with improved performance, optical properties of epilayers grown on different orientations of available substrates have to be better understood. Furthermore, most previous studies on the fundamental band structures of AlN have been carried out for heteroepilayers grown on sapphires, which are plagued by lattice mismatch induced strain and high threading dislocation density, which significantly inhibited our ability for precisely determining the fundamental band structure parameters of AlN. In this work, we report a systematic comparative study of optical properties of both homoepitaxial and heteroepitaxial layers of AlN grown on polar c-plane as well as a-plane and m-plane orientations probed by DUV photoluminescence ͑PL͒.AlN bulk single crystal substrates were produced by sublimation crystal growth using polycrystalline AlN wafer as seeds and have a thickness of about 1 mm and an average grain size of about 2 ϫ 3 mm 2 . 12 The surface of AlN bulk crystal substrates was prepared by chemical mechanical polishing ͑done by NovaSiC͒ that provided a surface roughness of about 1 -4 nm. The dislocation density i...

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confidence: 99%

Photoluminescence properties of AlN homoepilayers with different orientations

Sedhain

Nepal

Nakarmi

et al. 2008

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“…[5][6][7] In particular, several potential applications using AlN nanostructures have been proposed including gas sensors, field emission device, and nanoscale light-emitting diodes. [8][9][10][11] In the growth of nanomaterials, an appropriate substrate is essential to obtain high-quality well-aligned nanostructures.…”

mentioning

confidence: 99%

Stress and its effect on optical properties of AlN nanorods

Zhang

Ling

et al. 2009

The stress states in AlN nanorods deposited on Si and its effect on optical properties have been investigated by means of Raman scattering and photoluminescence methods. The observed frequency downshift and linewidth broadening from temperature-dependent Raman scattering can be well described by an empirical relationship taking into account the contributions of the thermal expansion and decay of optical phonons. The phonon-energy difference of the E 2 ͑high͒ mode between the stress-free bulk-AlN and AlN nanorods appears to increase with increasing temperature, demonstrating that differential thermal expansion between the Si-substrate and AlN nanorods is the key parameter reflecting the stress in the nanorods.

“…Using wide bandgap semiconductors as the active layer can reduce the number of filters required to suppress the unwanted radiation at large wavelengths. [3][4][5][6][7] Furthermore, an improved EUV hardness is observed in devices based on this compound.…”

mentioning

confidence: 88%

Extreme ultraviolet detection using AlGaN-on-Si inverted Schottky photodiodes

Malinowski

Duboz²,

Moor

et al. 2011

We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky diodes for extreme ultraviolet (EUV) detection. AlGaN layers were grown on silicon wafers by molecular beam epitaxy with the conventional and inverted Schottky structure, where the undoped, active layer was grown before or after the n-doped layer, respectively. Different current mechanisms were observed in the two structures. The inverted Schottky diode was designed for the optimized backside sensitivity in the hybrid imagers. A cut-off wavelength of 280 nm was observed with three orders of magnitude intrinsic rejection ratio of the visible radiation. Furthermore, the inverted structure was characterized using a EUV source based on helium discharge and an open electrode design was used to improve the sensitivity. The characteristic He I and He II emission lines were observed at the wavelengths of 58.4 nm and 30.4 nm, respectively, proving the feasibility of using the inverted layer stack for EUV detection.Extreme ultraviolet (EUV) detection is gaining increasing attention with recent developments in solar science and EUV lithography.