Textbook-like device characteristics are demonstrated in vertical GaN p-n diodes grown on bulk GaN substrates. These devices show simultaneously an avalanche breakdown voltage (BV) of >1.4 kV under reverse bias, an ideality factor plateau of $2.0 in a forward bias window followed by a near unity ideality factor of 1.1, which are consistently achieved over a temperature range of 300-400 K. At room temperature (RT), the diode with a mesa diameter of 107 lm showed a differential on-resistance R on of 0.12 mXcm 2 , thus resulting in a record figure-of-merit BV 2 /R on of $16.5 GW/cm 2 , which is the highest ever demonstrated in any semiconductors. Analytical models are used to fit experimental I-Vs; based on the recombination current with an ideality factor of $2.0, a Shockley-Read-Hall lifetime of 12 ns is extracted at RT with an estimated recombination center concentration of 3 Â 10 15 cm À3. V

We have used okadaic acid (OA), a cell-permeable inhibitor of serine/threonine protein phosphatase types 1 (PP-1) and 2A (PP-2A), to demonstrate that the subcellular distribution of glucocorticoid receptor (GR) in rat fibroblasts is influenced by its phosphorylation state. Nuclear GRs in OA-treated cells retain transcriptional enhancement activity. Nuclear import or export of hormone agonist-bound GRs is not affected by OA. However, a dose of OA that fully inhibits PP-2A and partially inhibits PP-1, but not a lower dose that only partially inhibits PP-2A, leads to inefficient nuclear retention of agonist-bound GRs, and their redistribution into the cytoplasm. These receptors appear to be trapped in the cytoplasmic compartment and are unable to recycle (i.e. reenter the nucleus). Addition of OA during different steps of GR recycling demonstrates that OA must be present during nuclear export of GRs to block GR recycling. A direct role for PP-1 and/or PP-2A in GR recycling is suggested by site-specific hyperphosphorylation of GRs in vivo during OA inhibition of recycling. These are the same sites that undergo in vitro site-specific dephosphorylation by PP-1 and PP-2A. The block in GR recycling that results from inhibition of PP-1 and/or PP-2A resembles effects previously observed in v-mos-transformed rat fibroblasts. Interestingly, OA inhibition of PP-2A in v-mos-transformed cells leads to the reversal of oncoprotein effects on GR recycling and retention of receptors within the nuclear compartment. We propose that GR recycling is influenced by the activities of distinct protein phosphatases (PP-1 and/or PP-2A), and that the interference of this pathway observed in v-mos-transformed cells may be the result of effects of the oncoprotein on the phosphatases or a specific subset of their targets.

We study the growth mode and strain state of GaN layers grown either directly on 6H–SiC(0001) or on thin (5 nm), coherently strained AlN nucleation layers. Using a combination of structural, optical, and vibrational characterization methods, we show that the 3.4% compressive lattice mismatch strain is fully relieved in the former case, whereas in the latter case a significant amount (0.3%) remains even after 1 μm of growth. This finding is clarified by in situ reflection high-energy electron diffraction and transmission electron microscopy. We demonstrate that the strain state of the GaN layer is determined by its growth mode, which in turn is governed by the degree of wetting of the underlayer rather than by lattice mismatch.

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In this letter, we present AlGaN/GaN lateral Schottky barrier diodes on silicon with recessed anodes and dual field plates. A low specific ON-resistance R ON,SP (5.12 m · cm 2 ), a low turn-ON voltage (< 0.7 V), and a high reverse breakdown voltage (BV) (>1.9 kV) were simultaneously achieved in devices with a 25-μm anode/cathode distance, resulting in a power figureof-merit BV 2 /R ON,SP of 727 MW · cm −2 . The record high BV of 1.9 kV is attributed to the dual field-plate structure.Index Terms-Schottky barrier diode, GaN on silicon, breakdown voltage, high voltage device, AlGaN/GaN, field plate. Manuscript

Single layer graphene is an ideal material for the base layer of hot electron transistors (HETs) for potential terahertz (THz) applications. The ultrathin body and exceptionally long mean free path maximizes the probability for ballistic transport across the base of the HET. We demonstrate for the first time the operation of a high-performance HET using a graphene/WSe van der Waals (vdW) heterostructure as a base-collector barrier. The resulting device with a GaN/AlN heterojunction as emitter, exhibits a current density of 50 A/cm, direct current gain above 3 and 75% injection efficiency, which are record values among graphene-base HETs. These results not only provide a scheme to overcome the limitations of graphene-base HETs toward THz operation but are also the first demonstration of a GaN/vdW heterostructure in HETs, revealing the potential for novel electronic and optoelectronic applications.

Glucocorticoid receptor (GR) nuclear translocation, transactivation and phosphorylation were examined during the cell cycle in mouse L cell fibroblasts. Glucocorticoid‐dependent transactivation of the mouse mammary tumor virus promoter was observed in G0 and S phase synchronized L cells, but not in G2 synchronized cells. G2 effects were selective on the glucocorticoid hormone signal transduction pathway, since glucocorticoid but not heavy metal induction of the endogenous Metallothionein‐1 gene was also impaired in G2 synchronized cells. GRs that translocate to the nucleus of G2 synchronized cells in response to dexamethasone treatment were not efficiently retained there and redistributed to the cytoplasmic compartment. In contrast, GRs bound by the glucocorticoid antagonist RU486 were efficiently retained within nuclei of G2 synchronized cells. Inefficient nuclear retention was observed for both dexamethasone‐ and RU486‐bound GRs in L cells that actively progress through G2 following release from an S phase arrest. Finally, site‐specific alterations in GR phosphorylation were observed in G2 synchronized cells suggesting that cell cycle regulation of specific protein kinases and phosphatases could influence nuclear retention, recycling and transactivation activity of the GR.