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In this paper, the electron mobility and sheet density of the two-dimensional electron gas (2DEG) in both air and argon environments at 600 °C were measured intermittently over a 5 h duration using unpassivated and Al2O3-passivated AlGaN/GaN (with 3 nm GaN cap) van der Pauw test structures. The unpassivated AlGaN/GaN heterostructures annealed in air showed the smallest decrease (∼8%) in 2DEG electron mobility while Al2O3-passivated samples annealed in argon displayed the largest drop (∼70%) based on the Hall measurements. Photoluminescence and atomic force microscopy showed that minimal strain relaxation and surface roughness changes have occurred in the unpassivated samples annealed in air, while those with Al2O3 passivation annealed in argon showed significant microstructural degradations. This suggests that cracks developed in the samples annealed in air were healed by oxidation reactions. To further confirm this, Auger electron spectroscopy was conducted on the unpassivated samples after the anneal in...

To research the lymphatic tropism and lymph cell apoptosis of cisplatin-nano carbon suspension in rats with the aim of proposing a new way for chemotherapy.A total of 72 Wistar rats were randomly divided into two groups. For the experimental group, cisplatin-nano carbon suspension 0.3 ml (4 mg/ml) was injected subcutaneously into Wistar rats' plantar. For the control group, cisplatin 0.3 ml (4 mg/ml) was injected intravenously. Cisplatin concentration in the inguinal lymphatic tissue and plasma was determined by high performance liquid chromatography (HPLC) at 1, 2, 3, 4, 5 and 6 hours after drug administration. The apoptosis of lymph cell was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay (TUNEL). Targeting ability were evaluated and compared by targeting index (TI), selecting index (SI) and relative extraction efficiency (RE). SPSS 17.0 statistical software was used to analyze the differentiation of the cisplatin concentration and apoptosis index (AI) among various groups. DAS software was used to evaluate the lymphatic tropism.The cisplatin concentration of lymphatic tissue in experimental group were respectively (1.03± 0.32), (3.00±0.91), (2.20±0.73), (1.56±0.38), (1.30±0.74) and (0.78±0.34)µg/g after administration 1, 2, 3, 4, 5 and 6 hours, while in control group were (0.49±0.21), (1.02±0.70), (0.59±0.50), (0.56±0.21), (0.47±0.18) and (0.36±0.13)µg/g, in which there were significant difference at every times (all P0.05)except at 1 hour(P = 0.173). The cisplatin concentration in plasma were significant higher in the experimental group than those in the control group at various times(all P0.05), the former were respectively (0.57±0.28), (1.22 ± 0.45), (0.61 ± 0.18), (0.51 ± 0.13), (0.45 ± 0.13) and (0.40 ± 0.07) µg/ml, while the latter were respectively (3.12±0.33), (4.09±0.48), (2.56±0.38), (2.05±0.13), (1.81±0.28) and (1.44±0.40) µg/ml. Values of TI were respectively 2.12, 2.93, 3.73, 2.78, 2.76 and 2.19 and SI were 1.80, 2.45, 3.63, 3.07, 2.86 and 1.93. Value of RE was 2.86. The AI in experimental group were respectively (16.5±5.2)%, (30.2±2.8)%, (51.7 ± 4.3)%, (69.8 ± 3.2)%, (80.1 ± 4.3)% and (89.7 ± 8.5)% , while in control group were respectively(1.3±0.8)%, (2.4±1.7)%, (3.2±1.1)%, (3.9±2.6)%, (5.1±2.1)% and (6.3±2.3)%, in which there were significant difference at every points(all P0.05).The nano carbon has the character of lymphatic tropism, and could send cisplatin to lymphatic tissue to achieve a higher concentration. The trait may break a new way for chemotherapy targeting lymph metastasis.

The development of radiation-hardened, temperature-tolerant materials, sensors and electronics will enable lightweight space sub-systems (reduced packaging requirements) with increased operation lifetimes in extreme harsh environments such as those encountered during space exploration. Gallium nitride (GaN) is a ceramic, semiconductor material stable within high-radiation, high-temperature and chemically corrosive environments due to its wide bandgap (3.4 eV). These material properties can be leveraged for ultraviolet (UV) wavelength photodetection. In this paper, current results of GaN metal-semiconductor-metal (MSM) UV photodetectors behavior after irradiation up to 50 krad and temperatures of 15°C to 150°C is presented. These initial results indicate that GaN-based sensors can provide robust operation within extreme harsh environments. Future directions for GaN-based photodetector technology for down-hole, automotive and space exploration applications are also discussed.

This paper reports the steady-state and transient temperature response of AlGaN/GaN high electron mobility transistor (HEMT) based structures. In this study, three localized heating schemes, namely, continuous self-heating, pulsed self-heating and heating with on-chip heaters are studied for sensor applications that require controlled heating profiles. Two scenarios were considered for the GaN sensor structure: 1) the silicon substrate under the AlGaN/GaN sensor is not removed, and 2) the silicon substrate is removed to form a suspended AlGaN/GaN diaphragm on which the sensor is located. The three heating schemes are analyzed by finite element thermal analysis, evaluated and compared. In addition, general guidelines for designing localized heating architectures for AlGaN/GaN HEMT based sensors are provided.

New milestones in space exploration can be realized through the development of radiation-hardened, temperature-tolerant materials, sensors and electronics. This enables lightweight systems (reduced packaging requirements) with increased operation lifetimes. Gallium nitride (GaN) is a ceramic, semiconductor material that is stable within high-radiation, high-temperature and chemically corrosive environments. Recently, this material platform has been utilized to realize sensors and electronics for operation under extreme harsh conditions. These devices exploit the two-dimensional electron gas (2DEG) formed at the interface between AlGaN/GaN heterostructures, which is used as the material platform in high electron mobility transistors (HEMTs). In this paper, a review of the advancements in GaN manufacturing technology such as the growth of epitaxially deposited thin films, micromachining techniques and high-temperature metallization is presented. In addition, the compelling results of fabricating and operating micro-scale GaNbased sensors within radiation environments and at elevated temperatures are shown. The paper will close with future directions GaN-based microsystems technology for down-hole, propulsion and space exploration applications.

The high-temperature characteristics (at 600 °C) of Ti/Al/Pt/Au multilayer contacts to gallium nitride (GaN) in air are reported. Microfabricated circular-transfer-line-method test structures were subject to 10 h of thermal storage at 600 °C. Intermittent electrical characterization during thermal storage showed minimal variation in the contact resistance after 2 h and that the specific contact resistivity remained on the order of 10−5 Ω-cm2. In addition, the thermally stored multilayer contacts to GaN showed ohmic I-V characteristics when electrically probed at 600 °C. The microstructural analysis with atomic force microscopy showed minimal changes in surface roughness after thermal storage. Observations of the thermochemical reactions after thermal storage using Auger electron spectroscopy chemical depth profiling showed diffusion of Pt and minimal additional Al oxidation. The results support the use of Ti/Al/Pt/Au multilayer metallization for GaN-based sensors and electronic devices that will operate within a high-temperature and oxidizing ambient.