Effect of Trap Behavior on the Reliability Instability of Metamorphic Buffer in InAlAs/InGaAs MHEMT on GaAs.

Our investigation focused on assessing the influence of the metamorphic buffer in metamorphic high-electron-mobility transistors (MHEMT) that were grown on GaAs substrates. While an MHEMT exhibited elevated off-state current levels, its direct current (DC) and radio frequency (RF) traits were found to be comparable to those of InP-based lattice-matched high-electron-mobility transistors (LM-HEMTs). However, the Pulsed I-V measurement results confirmed the presence of the fast transient charging effect, leading to a more substantial degradation in drain current observed in MHEMT. In addition, through the low-frequency noise characteristics, it was confirmed that the dominant trapping location was located in the bulk site. The slope of the 1/f noise measurement indicated that the primary trapping site was in proximity to the bulk traps. The carrier-number-fluctuation (CNF) model was employed to extract the bulk trap density (Nt). For the LM-HEMTs, the value was at 3.27 × 1016 eV-1·cm-3, while for the MHEMT, it was 3.56 × 1017 eV-1·cm-3.

Primary well differentiated hepatic liposarcoma in a meerkat (Suricata suricatta).

A 9-year-old female meerkat (Suricata suricatta) succumbed to progressive abdominal distension, anorexia, and depression. Necropsy revealed an extensively distended abdomen with ascites and markedly enlarged liver. The liver had multiple yellowish masses and displaced the thoracic cavity and abdominal organs. There was no evidence of metastatic lesions based on the gross and microscopic findings. Histologically, the liver mass was composed of locally invasive well-differentiated neoplastic adipocytes with Oil Red O-positive lipid vacuoles. Immunohistochemistry revealed positive immunoreactivity to vimentin, S-100 and negative to pancytokeratin, desmin, smooth muscle actin (SMA), ionized calcium-binding adapter molecule 1 (IBA-1). Thus, the primary well differentiated hepatic liposarcoma was diagnosed based on gross, histological and immunohistochemistry results.

Explicit Thermal Resistance Model of Self-Heating Effects of AlGaN/GaN HEMTs with Linear and Non-Linear Thermal Conductivity.

We presented an explicit empirical model of the thermal resistance of AlGaN/GaN high-electron-mobility transistors on three distinct substrates, including sapphire, SiC, and Si. This model considered both a linear and non-linear thermal resistance model of AlGaN/GaN HEMT, the thickness of the host substrate layers, and the gate length and width. The non-linear nature of channel temperature-visible at the high-power dissipation stage-along with linear dependency, was constructed within a single equation. Comparisons with the channel temperature measurement procedure (DC) and charge-control-based device modeling were performed to verify the model's validity, and the results were in favorable agreement with the observed model data, with only a 1.5% error rate compared to the measurement data. An agile expression for the channel temperature is also important for designing power devices and monolithic microwave integrated circuits. The suggested approach provides several techniques for investigation that could otherwise be impractical or unattainable when utilizing time-consuming numerical simulations.

A quantitative approach for trap analysis between Al0.25Ga0.75N and GaN in high electron mobility transistors.

The characteristics of traps between the Al0.25Ga0.75N barrier and the GaN channel layer in a high-electron-mobility-transistors (HEMTs) were investigated. The interface traps at the Al0.25Ga0.75N/GaN interface as well as the border traps were experimentally analyzed because the Al0.25Ga0.75N barrier layer functions as a dielectric owing to its high dielectric constant. The interface trap density Dit and border trap density Nbt were extracted from a long-channel field-effect transistor (FET), conventionally known as a FATFET structure, via frequency-dependent capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. The minimum Dit value extracted by the conventional conductance method was 2.5 × 1012 cm-2·eV-1, which agreed well with the actual transistor subthreshold swing of around 142 mV·dec-1. The border trap density Nbt was also extracted from the frequency-dependent C-V characteristics using the distributed circuit model, and the extracted value was 1.5 × 1019 cm-3·eV-1. Low-frequency (1/f) noise measurement provided a clearer picture of the trapping-detrapping phenomena in the Al0.25Ga0.75N layer. The value of the border trap density extracted using the carrier-number-fluctuation (CNF) model was 1.3 × 1019 cm-3·eV-1, which is of a similar level to the extracted value from the distributed circuit model.

Characterization of Electrical Traps Formed in Al2O3 under Various ALD Conditions.

Frequency dispersion in the accumulation region seen in multifrequency capacitance-voltage characterization, which is believed to be caused mainly by border traps, is a concerning issue in present-day devices. Because these traps are a fundamental property of oxides, their formation is expected to be affected to some extent by the parameters of oxide growth caused by atomic layer deposition (ALD). In this study, the effects of variation in two ALD conditions, deposition temperature and purge time, on the formation of near-interfacial oxide traps in the Al2O3 dielectric are examined. In addition to the evaluation of these border traps, the most commonly examined electrical traps-i.e., interface traps-are also investigated along with the hysteresis, permittivity, reliability, and leakage current. The results reveal that a higher deposition temperature helps to minimize the formation of border traps and suppress leakage current but adversely affects the oxide/semiconductor interface and the permittivity of the deposited film. In contrast, a longer purge time provides a high-quality atomic-layer-deposited film which has fewer electrical traps and reasonable values of permittivity and breakdown voltage. These findings indicate that a moderate ALD temperature along with a sufficiently long purge time will provide an oxide film with fewer electrical traps, a reasonable permittivity, and a low leakage current.

Role of early endourologic management of tuberculous ureteral strictures.

BACKGROUND AND PURPOSE: Tuberculous ureteral stricture causing progressive obstructive uropathy commonly complicates renal tuberculosis. The aim of our study was to evaluate the effectiveness of early ureteral stenting or percutaneous nephrostomy (PCN) in patients with tuberculous ureteral strictures. PATIENTS AND METHODS: Seventy-seven patients (84 renal units) with tuberculous ureteral strictures were analyzed. We evaluated the final outcome of involved kidneys with three different managements: medication only (N = 37), medication plus ureteral stenting (N = 28), or medication plus PCN (N = 19). RESULTS: The overall nephrectomy rate was 51%. In patients treated with medication only, the nephrectomy rate was 73%, whereas the nephrectomy rate was 34% in patients treated with medication plus early ureteral stenting or PCN. The rate of reconstructive surgery for ureteral strictures also was significantly different for patients treated with medication only (8%) and those receiving medication plus early ureteral stenting or PCN (49%). Spontaneous resolution of the strictures was noted in 6 of the 12 renal units that were managed with early ureteral stenting. CONCLUSIONS: Early ureteral stenting or PCN in patients with tuberculous ureteral strictures may increase the opportunity for later reconstructive surgery and decrease the likelihood of renal loss.