UV Detector based on InAlN/GaN-on-Si HEMT Stack with Photo-to-Dark Current Ratio > 107

We demonstrate an InAlN/GaN-on-Si HEMT based UV detector with photo to dark current ratio > 107. Ti/Al/Ni/Au metal stack was evaporated and rapid thermal annealed for Ohmic contacts to the 2D electron gas (2DEG) at the InAlN/GaN interface while the channel + barrier was recess etched to a depth of 20 nm to pinch-off the 2DEG between Source-Drain pads. Spectral responsivity (SR) of 34 A/W at 367 nm was measured at 5 V in conjunction with very high photo to dark current ratio of > 10^7. The photo to dark current ratio at a fixed bias was found to be decreasing with increase in recess length of the PD. The fabricated devices were found to exhibit a UV-to-visible rejection ratio of >103 with a low dark current < 32 pA at 5 V. Transient measurements showed rise and fall times in the range of 3-4 ms. The gain mechanism was investigated and carrier lifetimes were estimated which matched well with those reported elsewhere.Comment: 12 page

High Responsivity in Molecular Beam Epitaxy (MBE) grown \b{eta}-Ga2O3 Metal Semiconductor Metal (MSM) Solar Blind Deep-UV Photodetector

In this report, we demonstrate high spectral responsivity (SR) in MBE grown epitaxial \b{eta}-Ga2O3-based solar blind MSM photodetectors (PD). (-2 0 1)-oriented \b{eta}-Ga2O3 thin film was grown by plasma-assisted MBE on c-plane sapphire substrates. MSM devices fabricated with Ni/Au contacts in an interdigitated geometry were found to exhibit peak SR > 1.5 A/W at 236-240 nm at a bias of 4 V with a UV to visible rejection ratio > 105. The devices exhibited very low dark current < 10 nA at 20 V and showed no persistent photoconductivity (PPC) as evident from the sharp transients with a photo-to-dark current ratio > 103. These results represent the state-of-art performance for MBE-grown \b{eta}-Ga2O3 MSM solar blind detector

Thickness Dependent Parasitic Channel Formation at AlN/Si Interfaces

The performance of GaN-on-Silicon electronic devices is severely degraded by the presence of a parasitic conduction pathway at the nitride-substrate interface which contributes to switching losses and lower breakdown voltages. The physical nature of such a parasitic channel and its properties are however, not well understood. We report on a pronounced thickness dependence of the parasitic channel formation at AlN/Si interfaces due to increased surface acceptor densities at the interface in silicon. The origin of these surface acceptors is analyzed using secondary ion mass spectroscopy measurements and traced to thermal acceptor formation due to Si-O-N complexes. Low-temperature (5 K) magneto-resistance (MR) data reveals a transition from positive to negative MR with increasing AlN film thickness indicating the presence of an inversion layer of electrons which also contributes to parasitic channel formation but whose contribution is secondary at room temperatures

Impact of Next-Generation I/O Architectures on the Design and Performance of Network Servers

The increasing demand for scalable and highly-available network services has challenged computer architects to develop new I/O architecture for servers. The recently released InfiniBand industry standard, for instance, provides scalable bandwidth and protected I/O communication using the memory-mapped communication model and a channelbased switched fabric technology. Advanced device controllers incorporate processor and memory and can execute sophisticated I/O protocols locally. While accommodating the new I/O architecture within the traditional software framework is straightforward, there is little if any research to explore the server designs that are enabled by the new I/O architecture and their performance impact. This paper uses modeling and simulation to investigate the designperformance space for network servers in the presence of I/O switches, such as InfiniBand, and programmable devices. We propose and analyze a range of scenarios starting from providing conventional servers with high I/O bandwidth, to modifying servers to exploit user-level I/O and direct device-to-device communication, to re-designing the operating system to o#oad file system and networking functions from the host to programmable devices

Analysis of screw dislocation mediated dark current in Al0.50Ga0.50N solar-blind metal-semiconductor-metal photodetectors

We report on a billion-fold reduction in reverse-bias leakage current density (11.3 A/cm(2) to 8.5 nA/cm(2 )at 20 V) across Schottky contacts made to Al0.50Ga0.50N epilayers grown on sapphire. Interdigitated back-to-back Ni/Au Schottky contacts were made to unintentionally doped Al0.50Ga0.50N epilayers grown by metal organic chemical vapor deposition to realize photodetectors with metal-semiconductor-metal geometry. Testing on a self-con-sistent series of samples grown under different conditions revealed that a two-order reduction in screw dislocation density is primarily responsible for the significant reduction in the lateral leakage (dark) current. This observation is validated by conducive atomic force microscopy experiments. Analytical modelling by temperature-dependent current-voltage measurements confirm a screw dislocation mediated carrier transport mechanism. The anomalously high reverse-bias leakage current (mu A-mA) in the highly defective samples is found to be dominated by thermionic field emission (TFE) at low biases and Poole-Frenkel emission (PFE) from a deep donor level at high biases. With a significant improvement in the crystalline quality, a solar-blind photodetector with an EQE of 47%, photo/dark current ratio of 1.4 x 10(5) and transient characteristics of < 20 ms is demonstrated. This study towards understanding the leakage in Al0.50Ga0.50N is expected to benefit the development of various deep-UV devices and GaN-AlGaN based power transistors

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Not AvailableLaser leveling of irrigated field promotes efficient utilization of water. In order to scientificallyunderstand the benefits and effects of laser leveling, experimental studies were carried out at selected sites in Moga and Ludhiana districts of Central Punjab region. The survey conducted at farmer’s fiel d in Moga district indicated27 % of water saving for paddy and wheat crops by laser leveling. The moisture measurement studies carried out in paddy and wheat grown campus field plots in Punjab Agricultural University campus, Ludhiana shows uniformmoisture content at 12 locations within a laser leveled plot in comparison to non laser leveled plotNot Availabl