Electrical properties of n-type GaSb substrates and p-type GaSb buffer layers for InAs/InGaSb superlattice infrared detectors

Lightly doped n-type GaSb substrates with p-type GaSb buffer layers are the preferred templates for growth of InAs/InGaSb superlattices used in infrared detector applications because of relatively high infrared transmission and a close lattice match to the superlattices. We report here temperature dependent resistivity and Hall effect measurements of bare substrates and substrate-p-type buffer layer structures grown by molecular beam epitaxy. Multicarrier analysis of the resistivity and Hall coefficient data demonstrate that high temperature transport in the substrates is due to conduction in both the high mobility zone center Γ band and the low mobility off-center L band. High overall mobility values indicate the absence of close compensation and that improved infrared and transport properties were achieved by a reduction in intrinsic acceptor concentration. Standard transport measurements of the undoped buffer layers show p-type conduction up to 300 K indicating electrical isolation of the buffer layer from the lightly n-type GaSb substrate. However, the highest temperature data indicate the early stages of the expected p to n type conversion which leads to apparent anomalously high carrier concentrations and lower than expected mobilities. Data at 77 K indicate very high quality buffer layers

Deep Centers In Semi-Insulating Current Topics In Solid State Physics Fe-Doped Native GaN Substrates Grown By Hydride Vapour Phase Epitaxy

Electrical properties, Fe concentration, and deep centers in semi-insulating Fe-doped GaN substrates grown by hydride vapor phase epitaxy (HVPE) were characterized by temperature-dependent Hall-effect measurements, secondary ion mass spectroscopy, and thermally stimulated current (TSC) spectroscopy, Five adjacent samples from a low-[Fe] wafer displayed very high resistivity, dominated by a center at 0,94 eV. At least six traps were observed in the samples by TSC, with trap (0.56-0.60 eV) being dominant. A metastable trap A, at similar to 0.82 eV appeared after white-light illumination at 300 K-A sample from a high-[Fe] wafer displayed a lower resistivity, dominated by a center at 0,58 eV. The largest TSC peak in this sample was trap A(1), although trap B also appeared. These TSC traps are compared with deep-level-transient- spectroscopy traps reported in conductive epitaxial and bulk HVPE-GaN

Deep Centers In Semi-Insulating Current Topics In Solid State Physics Fe-Doped Native GaN Substrates Grown By Hydride Vapour Phase Epitaxy

Electrical properties, Fe concentration, and deep centers in semi-insulating Fe-doped GaN substrates grown by hydride vapor phase epitaxy (HVPE) were characterized by temperature-dependent Hall-effect measurements, secondary ion mass spectroscopy, and thermally stimulated current (TSC) spectroscopy, Five adjacent samples from a low-[Fe] wafer displayed very high resistivity, dominated by a center at 0,94 eV. At least six traps were observed in the samples by TSC, with trap (0.56-0.60 eV) being dominant. A metastable trap A, at similar to 0.82 eV appeared after white-light illumination at 300 K-A sample from a high-[Fe] wafer displayed a lower resistivity, dominated by a center at 0,58 eV. The largest TSC peak in this sample was trap A(1), although trap B also appeared. These TSC traps are compared with deep-level-transient- spectroscopy traps reported in conductive epitaxial and bulk HVPE-GaN

Treatment with Low-Dose Cytarabine in Elderly Patients (Age 70 Years or Older) with Acute Myeloid Leukemia: A Single Institution Experience

International audienceOBJECTIVES: Low-dose cytarabine (LD-AraC) is still regarded as the standard of care in elderly patients with acute myeloid leukemia (AML) 'unfit' for intensive chemotherapy. In this study, we reported our experience with LD-AraC in patients \textgreater/= 70 years old and compared the results to those of intensive chemotherapy, best supportive care (BSC), or hypomethylating agents in the same age population. METHODS: Between 2000 and 2014, 60 patients received LD-AraC at 20 mg once or twice daily by subcutaneous injection for 10 consecutive days every 4-6 weeks. RESULTS: Complete remission rate with LD-AraC was 7% versus 56% with intensive chemotherapy and 21% with hypomethylating agents. Median overall survival (OS) of patients treated with LD-AraC was 9.6 months with 3-year OS of 12%. Survival with LD-AraC was better than with BSC only (P = 0.001). Although not statistically significant, intensive chemotherapy and hypomethylating agents tended to be better than LD-AraC in terms of OS (median: 12.4 months and 16.1 months, respectively). There was no clear evidence that a beneficial effect of LD-AraC was restricted to any particular subtype of patients, except for cytogenetics. There was a trend for a better OS in LD-AraC treated patients in the setting of clinical trials as compared with those treated outside of a clinical trial. CONCLUSIONS: Despite a trend in favor of intensive chemotherapy and hypomethylating agents over LD-AraC, no real significant advantage could be demonstrated, while LD-AraC showed a significant advantage comparatively to BSC. All this tends to confirm that LD-AraC can still represent a baseline against which new promising agents may be compared either alone or in combinatio

Treatment patterns and comparative effectiveness in elderly acute myeloid leukemia patients (age 70 years or older): the Lyon-university hospital experience

International audienceThe treatment of very elderly patients (\textgreater/=70 years) with acute myeloid leukemia remains controversial. We present here 302 patients seen over a 14-year period in order to understand the real-world treatment patterns and outcomes in this patient population. Less than 25% of patients achieved a complete remission. The median overall survival was 12.4, 11.5 and 2.6 months, with a 3-year rates of 27%, 17% and 6%, for non-acute promyelocytic leukemia patients receiving intensive chemotherapy, lower-intensity therapy or best supportive care (BSC), respectively. In all ages, results were not significantly different among patients receiving low-intensity therapy and intensive chemotherapy, but significantly worse in those treated with BSC only. Similarly, intensive chemotherapy and low-intensity therapy gave better survival rates than BSC in patients with favorable- or intermediate-risk cytogenetics and in those with unfavorable cytogenetics (p \textless 0.0001 and p = 0.04, respectively

Graphene-Based Test Platform in Potential Application for FET with Guanine as Gate Dielectric

Guanine and poly(methyl methacrylate) (PMMA) layers 60 nm thick were fabricated by physical vapor deposition and spin-coating, respectively, for potential application as bio-based field-effect transistors. A few layers of graphene on a variety of non-flexible and flexible supports were used as substrates for the guanine and PMMA layers. The interactions between these layers and graphene were studied and their effects on the electrical properties of the graphene were monitored over an extended period of time. Guanine had no noticeable effects on the transport properties of graphene. The presence of PMMA reduced the charge-carrier mobility of graphene by up to 42%. This combination has potential for use as a device in biosensors, environmental science, computer-processing, and graphene-based electronics