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Polarization-induced p-type doping is realized in molecular beam epitaxy (MBE) grown ultrathin body GaN/AlN heterostructures. The novel heterostructure consisting of a thin strained GaN layer grown on an AlN template exhibits a hole gas density close to the interface polarization charge (~5 × 1013 /cm2). Both enhancement- and depletion-mode (E/D) p-channel heterostructure field effect transistor (HFETs) are demonstrated. Driven by the high hole density, a 2.4-μm-long D-mode HFET with alloyed ohmic contacts shows improvement of drain current from 150 mA/mm (VGS = 12 V, VDS = 30 V) at 300 K to 270 mA/mm (VGS = 15 V, VDS = 30 V) at 77 K. The extrinsic peak transconductance of the D-mode device increases from 11 mS/mm (VGS = 6 V, VDS = 30 V) at 300 K to 16 mS/mm (VGS = 4 V, VDS = 30 V) at 77 K. Both the drive current and transconductance are recorded in nitride p-channel FETs. MBE regrown heavily Mg-doped p+-GaN is then employed for ohmic contacts of E-mode p-channel HFETs. A 2-μm-long E-mode device with a drain current of 4 mA/mm (VGS = 10 V, VDS = 80 V) and ON/OFF current ratio of 103 is achieved.

Background & objectives: Psoriasis is a recurrent hyper-proliferative skin disease which is often associated with free radical generation, abnormal lipid metabolism and increased inflammatory secretion that induce cardiovascular risk in these patients. The present study was intended to evaluate serum lipids, lipoprotein and oxidants-antioxidants status and to establish their relationship with atherogenic risk markers [oxidized low-density lipoprotein (oxLDL) and high-sensitivity C-reactive protein (hsCRP)] in patients with psoriasis. Methods: The study was conducted on 150 psoriasis patients and 150 age- and sex-matched healthy controls. Overnight fasting blood samples were obtained for lipids, lipoproteins, lipid oxidation and peroxidation products [oxLDL, malondialdehyde (MDA)], antioxidant enzymes [reduced glutathione (GSH) and total antioxidant status] levels and hsCRP estimations. Results: The mean levels of atherogenic lipids [total cholesterol (P

Realization of steep sub-threshold slope (SS) transistors requires exploiting carrier transport mechanisms such as tunneling [1], and also alternative gate barrier materials (i.e. ferroelectric materials) with internal voltage gain [2]. Theoretical studies on piezoelectric barriers indicate that it is possible to achieve internal voltage amplification and steep SS in GaN MOSHEMTs by utilizing electrostriction in conjunction with piezoelectricity in AlN and InAlN [3] [4]. Less than 60 mV/decade SS was experimentally observed in GaN MOSHEMTs with InAlN barriers, in which the steep transition was tentatively correlated with the inhomogeneous distribution of polarization in the barrier [5]. However, steep SS were only observed at drain current (I d ) near nA/mm regimes, which leads to difficulties in interpretation of experiment data. Understanding of the mechanism of the steep SS in these devices is still unclear and needs more characterization and modeling. In this work we demonstrate InAlN/AlN/GaN MOSHEMTs with less than 60 mV/decade SS in deep sub-threshold regions (1E-8 A/mm and below) at room temperature (RT). Drain voltage and temperature dependent characteristics are provided with analysis for advancing our understanding of this phenomenon.

This article was migrated. The article was not marked as recommended. Introduction: Although evidence based medicine (EBM) is part of undergraduate training in several countries, Indian medical schools are yet to make a meaningful start. We report our experience with EBM training for undergraduate. Methods: Third year students undergoing clinical clerkship at a teaching hospital underwent an 8 week course on EBM with modules on concepts, formulating questions, searching for evidence and critical appraisal. Feedback was taken and assessment done on knowledge and searching skills. Results: 90% of students had poor awareness of EBM. 92% considered evidence the most important component of EBM; 5% considered clinical expertise and patient values as part of EBM. At baseline majority cited Google the most reliable search tool. Only 27% felt EBM relevant to their curriculum. 66% rated the course good, very good or excellent. Hands-on training enhanced learning lack of background knowledge of diseases hindered it. Conclusion: Awareness of EBM is low among undergraduates and most find it irrelevant to their curriculum. Our experience suggests that it is feasible to integrate EBM training into undergraduate curriculum. More studies reporting knowledge and skills before and after EBM courses would strengthen the cause for making it part of undergraduate medical curriculum in India.

The origin and management of DC-RF dispersion in InAlN-based GaN high electron mobility transistors (HEMTs) is examined, in conjunction with consideration of the implications for device speed. This study, in which GaN HEMTs with alloyed and non-alloyed ohmic contacts are compared, renders the following observations and hypotheses: 1) We show and explain that dispersion free operation can be achieved without passivation. 2) The root cause of dispersion associated with surface states is often introduced during device processing; in particular, unintentional or un-optimized oxidation of the HEMT surface. 3) These undesired surface states also lead to gate extension (virtual gate), which decreases device speed but increases the breakdown voltage. In addition, the function and efficacy of a plasma-based ultrathin passivation is evaluated.

Pityriasis rosea is an acute self-limiting papulosquamous skin disorder of unknown etiology. Although pityriasis rosea is a common dermatologic disorder, information regarding the epidemiology of the disease in India is limited because of inadequate studies. The incidence and presentation of pityriasis rosea varies from one geographical region to another. The objective was to study the various clinical patterns of the disease and epidemiologic factors influencing its occurrence. A cross-sectional study on the clinicoepidemiologic pattern of pityriasis rosea was conducted. A detailed history of illness regarding onset, evolution, duration, symptoms, systemic features, recurrence, history of contact, and associated factors such as socioeconomic status, history of drug intake, and use of new clothing, along with epidemiologic data, was recorded in the performa. The age of the patients ranged from 3 to 47 (mean 20.32) years. Incidence of pityriasis rosea was highest among patients aged 11 to 20 years followed by those 21 to 30 years. There was a male preponderance. Seasonal variation was not evident. History of using new garments or old garments, unwashed for an extended period was elicited in 23% of cases. The average interval of onset of lesions and presentation to physician was 14.45 days. Pruritus was a common symptom (70%). Of 73 patients, 67 had herald patch. The clinical features of most of the cases were in accordance with the classical pattern of pityriasis rosea.

Atomic layer deposited (ALD) high band gap (∼6.5eV) [1], high k (∼9.1) Al 2 O 3 has emerged as an attractive candidate to support vertical scaling of AlN/GaN HEMTs [2] and its variants owing to its outstanding dielectric, thermal, and chemical properties. Integration of ALD oxides with GaN will enable lower gate leakage currents, high breakdown voltages, and surface passivation. In this work we present a comprehensive characterization of AlN/GaN MOS-HEMT gate stacks with ALD Al 2 O 3 of various thicknesses. Through capacitance-voltage and Hall-effect measurements, we find the presence and propose an origin of benign donor-type interface charge (Q int ) at the AlN/Al 2 O 3 junction, and relate its presence to the polarization charges in AlN. By studying tunneling transport in corresponding (Ni/Al 2 O 3 /Ni) M-I-M diodes, we extract the Ni/Al 2 O 3 surface barrier height (Ф B ), the electron tunneling effective mass in Al 2 O 3 , and discuss the resulting HEMTs.

Silicon substrates offer an attractive substrate platform for GaN RF and power electronics. In this work, we address the key challenges and provide solutions for the RF-MBE growth of GaN high-electron-mobility transistors (HEMTs) on Si(111). Moreover, by developing low-leakage buffer layers and employing raised source/drain regrown ohmic contacts, high-performance HEMTs are realized at a significantly lower process temperature by plasma MBE than by MOCVD. This is expected to motivate further ideas for the integration of GaN with silicon that go beyond RF and power electronics into the regime of low-power digital logic by exploiting the unique polarization properties of GaN.

Double heterostructures of strained GaN quantum wells (QWs) sandwiched between relaxed AlN layers provide a platform to investigate the quantum-confined electronic and optical properties of the wells. The growth of AlN/GaN/AlN heterostructures with varying GaN quantum well thicknesses on AlN by plasma molecular beam epitaxy (MBE) is reported. Photoluminescence spectra provide the optical signature of the thin GaN QWs. Reciprocal space mapping in X-ray diffraction shows that a GaN layer as thick as ∼28 nm is compressively strained to the AlN layer underneath. The density of the polarization-induced two-dimensional electron gas (2DEG) in the undoped heterostructures increases with the GaN QW thickness, reaching ∼2.5 × 1013/cm2. This provides a way to tune the 2DEG channel density without changing the thickness of the top barrier layer. Electron mobilities less than ∼400 cm2/Vs are observed, leaving ample room for improvement. Nevertheless, owing to the high 2DEG density, strained GaN QW field-effect transis...

Superior electronic and thermal properties have made InAlN/GaN high-electron-mobility transistors (HEMTs) an attractive candidate for power electronics applications. However, their high gate leakage current remains a serious challenge affecting the reliability and performance of these heterostructures. Leakage paths through dislocations or by percolation through inhomogeneities in the InAlN alloy barrier restrict the voltage handling capability of these HEMTs. In this work, we show that surface treatment with KOH greatly reduces the gate leakage current. Consequently, the switching characteristics of the HEMTs improve, and they exhibit lower subthreshold slopes and improved breakdown characteristics. The finding should be of interest for both microwave and power electronics applications of nitride HEMTs.

CASE REPORT A 40­year­old female presented to the dermatology OPD with an ulcerating growth of the left upper eyelid for the last three years. The growth was gradually increasing in size. On examination, there was an irregular erythematous swelling involving the whole of left upper eyelid with ulceration and areas of necrosis in the lateral part. A provisional diagnosis of sebaceous gland carcinoma was made. A biopsy of the eyelid growth was advised to confirm the diagnosis. Along with eyelid lesion, numerous asymptomatic, darkly pigmented papules were discovered over the face, trunk and extremities. These were more over the flexures like the neck, axilla, sub­mammary area and groin (Figures 1, 2). On being questioned about the lesions, the patient said that these lesions have appeared rapidly over a period of last six months. Detailed haematological, biochemical investigations, chest X­ray, upper gastrointestinal endoscopy, lower gastrointestinal endoscopy, mammography, abdominal ultrasound and bone marrow examination failed to reveal evidence of any systemic malignancy. Based on the clinical findings, a diagnosis of Lesser–Trelat sign in association with skin malignancy was made. The patient was referred to CLINICAL IMAGES OPEN ACCESS

Lattice-matched InAlN/AlN/GaN high electron mobility transistors offer high performance with attractive electronic and thermal properties. For high-voltage applications, gate leakage currents under reverse bias voltages remain a serious challenge. This current flow is dominated by field enhanced thermal emission from trap states or direct tunneling. We experimentally measure reverse-bias gate leakage currents in InAlN/AlN/GaN transistors at various temperatures and find that the conventional trap-assisted Frenkel-Poole model fails to explain the experimental data. Unlike the non-polar semiconductors Si, Ge, large polarization-induced electric fields exist in III-nitride heterojunctions. When the large polarization fields are accounted for, a modified Frenkel-Poole model is found to accurately explain the measured data at low reverse bias voltages. At high reverse bias voltages, we identify that the direct Fowler-Nordheim tunneling mechanism dominates. The accurate identification of the gate leakage curren...

Unlike silicon and traditional III-V semiconductors, the III-nitrides exhibit high spontaneous and piezoelectric polarization charges at epitaxial polar heterojunctions. In the process of investigating scaling properties of gate-stacks consisting atomic-layer deposited Al2O3/III-Nitride heterojunctions, we find interface charges that appear closely linked to the polarization charges of the underlying nitride substrate. Through capacitance-voltage measurement on a series of samples of varying dielectric thicknesses, we find the presence and propose an origin of benign donor-type interface charges (Qit ∼6 × 1013 cm−2) at the AlN/Al2O3 junction. This interface charge is almost equal to the net polarization charge in AlN. The polarization-related dielectric/AlN interface charge and the role of oxygen in the dielectric as a possible modulation dopant potentially offer opportunities for various device applications.

Xanthoma disseminatum (XD) is a rare subtype of non-Langerhan's cell histiocytosis (non-LCH). To date, just greater than 100 cases of XD have been reported; however, association with hyperlipidemia is extremely rare. We present a unique case of XD associated with familial hypertriglyceridemia (FHTG). Additionally, the patient had an extensive Koebner response.