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The material and electrical properties of GaN-based light-emitting diodes (LEDs) grown on wet-etched stripe-patterned substrates were investigated. Footprint-like patterns, located directly above the inclined groove sidewalls, were found on the as-grown LED surface. Cross-sectional transmission electron microscopy (TEM) showed that ‘tumor’-like structures with poor crystal quality were initiated on the inclined sidewalls, seeding dislocation bundles in the subsequently grown crystal. The high dislocation density slowed down the growth above the inclined sidewall, resulting in the uneven morphology. The fabricated devices showed over 30% enhancement in light output power as a result of improvements in both internal and extraction efficiencies.

We studied electrodeless photoelectrochemical (ELPEC) etching of GaN in a K2S2O8/KOH solution irradiated either continuously or periodically with ultraviolet (UV) light. The rate of recombination of electrons and holes at dislocation defects is greater than for crystalline GaN. The ELPEC etching with a continuous UV light resulted in a selective etching between dislocations and crystalline GaN and a rough etched surface. To reduce the recombination of the photo-generated carriers, the GaN was irradiated with periodical UV light modulated by a chopper during ELPEC etching. The shorter the interval of UV irradiation, the smoother is the etched GaN surface. A uniform and smooth etched surface was obtained with a root-mean-square (RMS) roughness 0.37 nm in solution (0.01 M KOH, 0.05 M K2S2O8) with a chopper frequency 2500 Hz. The p-GaN etching was also realized by ELPEC etching with a chopped UV source (ELPEC-CS etching) using an Au mask in K2S2O8/KOH solution. The etching rate of p-GaN was 2.8 nm/min at a chopper frequency of 3000 Hz and a power intensity of 63 mW/cm−2 in solution (0.5 M KOH, 0.05 M K2S2O8).

Photoelectrochemical (PEC) etching technique has been proven to be an effective method to etch GaN. Despite its success, investigations on etching-induced damage are still scare. In this work, the damage induced by PEC etching of GaN in KOH electrolyte was studied. Photoluminescence (PL) spectroscopy was used to explore the origin of etching-induced damaged layer. From the variable temperature PL measurements, the origin of etching-induced damage was attributed to be the defect complex of VGa-ON (gallium vacancy bonds to oxygeon on nitrogen antisite). With determination of the defect origin, the electronic transition in the etch damage-related yellow luminescence (YL) band was suggested to be deep donor-like state to shallow-acceptor transition. In addition, a post-treatment method with boiled KOH chemical etching was developed to remove the thin damaged layer. In this method, crystallographic etching characteristics of boiled KOH was observed to assist in the formation of smooth sidewall facets. As revealed by the reduction of yellow luminescence, we propose this novel technique as a near damage-free etching method.

Damage-free etching of GaN by Cl2, assisted by an ArF (193 nrm) excimer laser, is demonstrated. At low temperatures, photo-assisted etching can provide a better etch rate and largely improve the surface morphology and quality. AFM results show that the etched GaN surface is obtained with a root-mean-square roughness of 1.7 nm. As compared with the photoluminescence spectra of photoelectrochemical wet etched GaN, the photo-assisted cryogenic etching is proved to be a damage-free dry etching technique.

The intrinsic response of quantum dash lasers are measured using a pulse optical modulation technique. Our results show fast well-to-dash carrier capture and intra-dash carrier relaxation with K-factors independent on the pump wavelengths.

We demonstrate bandgap tuned InAs/InAlGaAs quantum-dash-in-well lasers grown on InP material using postgrowth quantum heterostructure intermixing. Compared to the control (non-intermixed) lasers, the light-current characteristics of lasers with emission wavelength tuned by over 100 nm shows insignificant changed suggesting that the quality of the intermixed material is well-preserved.

Three LOCOS-type isolations, viz. modified Scaled LOCOS (MSL), Sidewall Sealed MSL (SSMSL), and Recessed SSMSL (RSSMSL) are evaluated for the 0.6 /spl mu/m-pitch isolation of 256 Mbit DRAM. About 4000 /spl Aring/ field oxide grown in a 1100/spl deg/C wet ambient is found to be optimal for field oxide thinning and bird's beak "punch-through" effects. At a given pad oxide thickness of 100 /spl Aring/ the end-of-line encroachment is the largest for MSL isolation, which essentially rules out MSL as a possible candidate. Although both SSMSL and RSSMSL have similarly good isolation characteristics and diode leakages, only RSSMSL has the undesirable subthreshold double-hump effect and reduced gate oxide integrity, both of which are due to the sharp corners associated with the silicon recess etch of the RSSMSL structure. Therefore, for the three structure studied, only SSMSL is a viable candidate for the 0.6 /spl mu/m-pitch isolation of 256 Mbit DRAM.

Lymphoblastic lymphoma (LBL) frequently affects young adults and usually presents with a mediastinal mass as well as bone marrow involvement. Although the frequency of LBL in the Far East is higher than that of Western countries, no reports regarding treatment of this disease have as yet been reported. We herein report our treatment experience and verify the efficacy of the Stanford/Northern California Oncology Group (NCOG) protocol for this disease and recommend treatment strategies for LBL patients. We retrospectively reviewed the medical records of adult LBL patients treated in our hospital from 1986 to 1996. Twenty-seven patients were diagnosed to have LBL. These patients' ages ranged from 17 to 73 years old with a median of 23. Nineteen patients had an initial stage IV disease. Of the 23 cases in which immunological studies were performed, 20 proved to be of T cell lineage, 1 of B cell type, and the other 2 lacked both T and B markers. Three major chemotherapeutic regimens including prednisone, methotrexate, doxorubicin, cyclophosphamide, etoposide-mechlorethamine, vincristine, procarbazine, prednisone (ProMACE-MOPP), cyclophosphamide, hydroxydaunomycin, vincristine, prednisone (CHOP), and the Stanford/NCOG protocol were used to treat 3, 6, and 15 patients, respectively. Two other patients were treated with two different chemotherapeutic regimens, respectively. One patient was excluded for analysis because of initial treatment by surgery. The complete response (CR) rates with ProMACE-MOPP, CHOP, and the Stanford/NCOG regimens were 0%, 17%, 80% and median overall survival 9, 8.5, and 15 months, respectively. Five patients with stage II-III diseases achieved long-term disease-free survival of 11–36 months with the Stanford/NCOG protocol with a median follow-up of 24 months. Four patients in late stage or relapse received allogeneic bone marrow transplantation (BMT). Two of them obtained long-term disease-free survival. Two other patients in CR were treated with high-dose chemotherapy (HDCT) supported with autologous BMT and peripheral blood stem cell transplantation (PBSCT), respectively. The patient receiving HDCT with autologous PBSCT died of LBL relapse 6 months after transplantation. The other patient undergoing HDCT with autologous BMT died of fulminant hepatitis 5.5 months after transplantation. The median overall survival of all these 26 patients was 12 months. B symptoms and treatment without the Stanford/NCOG protocol were found to have significantly negative impacts on both patients' overall and progression-free survivals. Our results suggest that the Stanford/NCOG protocol may be an effective chemotherapy for adult LBL and may provide long-term remission for patients in an early stage of disease. For those patients with LBL in an advanced stage or in relapse, HDCT with allogeneic or autologous BMT is probably the treatment of choice.

Ethambutol is a useful first line antituberculous drug, but can cause significant visual impairment. In order to determine the clinical manifestations of optic neuropathy associated with ethambutol, and the margin of drug safety in Koreans, we investigated ten men and four women, diagnosed between 1995 and 1997 at Seoul Municipal Boramae Hospital as suffering from ethambutol toxicity. After determining their history, including the period during which ethambutol had been administered, and its dose, a complete eye examination was performed, including measurement of best-corrected visual acuity, pupillary examination, color vision, fundus examination and a test of visual field. Ocular ethambutol toxicity was observed at a dose as low as 12.3 mg/kg. Abnormal ophthalmic findings include decreased visual acuity and abnormal visual field, especially in the central scotoma, and abnormal color perception. In conclusion, ethambutol at a low dose can cause optic neuropathy, and for the early detection of this, a color vision test is important.

4154 Background: Tolerance and outcomes of HIV+ anal cancer patients are questioned, especially since the emergence of High Active Anti-Retroviral Therapy (HAART) in the mid-1990s. Our experience in treating these patients before and during the HAART era is reported. Methods: From 1987–2003, 19 HIV+ invasive anal cancer patients were treated with: 30–60 Gy pelvic RT (2 Gy/d) + Mitomycin C (10 mg/m2 bolus on d1) + 5-FU (1000 mg/m2/d, continuous infusion d1–4 and 28–31). Results: Mean CD-4 count at cancer diagnosis was 311, with 9 on HAART. Mean CD-4 count for HAART was 383 and 247 for non-HAART. Stage distribution: 1 T1, 9 T2, 9 T3, 18 N0, 1 N3. Mean f/u was 40 months. 79% had complete response after chemoRT. 4 had locally persistent disease. There was 1 loco-regional recurrence and 2 distant metastases. 79% of the cohort is colostomy-free. Median OS has not been reached. OS at 2 and 3 years were: 88%and 79%, with 10 Alive and NED, 1 Alive with disease, 3 Dead of disease, 5 Dead from intercurrent disease (all secondary to AIDS). 1.5 year DFS was 74%. Break and CD-4 count < 200 had a statistically significant negative impact on DFS, but not OS. HAART did not affect either factor. 11 had RT break for median of 17 days. There was no Grade 4 skin toxicity. All completed the 2nd 5-FU cycle: 7 had delay (median 7 days) and 3 had dose decrease. There were 6 hospitalizations: 5 neutropenic fevers and 1 perineal abscess rupture. WBC Toxicity: 6-Grade 3 and 2-Grade 4. Platelet Toxicity: 2-Grade 3. Heme toxicity was not affected by HAART or CD4 count < 200. There were no treatment related deaths. Conclusion: HIV+ anal cancer patients have reasonable tolerance and outcomes with chemoRT. CD-4 count < 200 and break were negative prognostic factors for DFS. Our 79% colostomy free survival is similar to RTOG 9208, where suboptimal control was attributed to mandatory RT break. Factors influencing break include heme and skin toxicity. To improve the therapeutic ratio, substitution of Mitomycin-C with Cisplatin, IMRT, and Ethyol are being explored. No significant financial relationships to disclose.

5609 Background: Traditional tx for locally advanced squamous cell carcinoma [SCC] of oropharynx [OPX] has been oncologic resection + adjuvant RT. In recent years, organ preserving therapy with che...

5619 Background: Randomized trials have reported improved outcome by adding chemotherapy to radiation, but none have examined concurrent chemoradiation with and without adjuvant chemotherapy. This retrospective analysis seeks to review our experience. Methods: Records of 29 consecutively treated patients from 1997 to 2002 were reviewed; these included stage IIII(n=8) and stage IV(n=21) patients with a median age of 49years. All patients received concurrent chemoradiation with the majority (82.8%) receiving at least three courses of cisplatin(100mg/m2;days1,22,43). Seventeen patients received adjuvant chemotherapy with cisplatin(80mg/m2;day1) and fluorouracil(1000mg/m2/d;days1–4) every 4 weeks, with a majority(82.4%) receiving at least three courses. Twelve patients did not receive adjuvant chemotherapy. All patients received radiotherapy in 1.8–2.0 Gy/d fractions to 7020Gy median total dose. Results: After a median follow-up of 39.6 months, seven of 29 patients had recurrent(n=6)/persistent disease(n=1). ...

The design, fabrication, and characteristics of a 350-V, 100-A buried-gate static induction transistor (SIT) as a power switching device for applications in military and space environments because of its potential for radiation hardness, high-frequency operation, and the incorporation of on-chip smart power sensor and logic functions are described. The potential radiation hardness of this class of devices was evaluated by measurement of SIT characteristics after irradiation with 100-Mrad (2-MeV) electrons and up to 10/sup 16/ fission neutrons/cm/sup 2/. High-temperature operation and the possibility of radiation damage self-annealing are discussed. >

The measured short-circuit current density in bifacial dendritic web silicon solar cells has been found to decrease with decreasing base resistivity, particularly under back illumination. In addition, the ratio of short-circuit current under back illumination to short-circuit current under front illumination was observed to vary with light intensity. These observations reflect the fact that the minority-carrier lifetime in the base of these cells is a function of the base resistivity and the illumination level. The dopant was assumed to play only an indirect role in determining lifetime. This decrease in lifetime is shown to follow from a distribution of defect levels in the bandgap. These levels are a consequence of extended defects that have been observed in the web material, namely oxide precipitates and the dislocation cores that they decorate. The dopant, acts only in the indirect role of moving the Fermi level over an existing background distribution of defect levels that arise from the extended defects. Assuming a parabolic distribution of defect levels in the bandgap, the minority-carrier lifetime was calculated as a function of doping density and excess carrier concentration (illumination level) using the Shockley-Reed-Hall theory. The short-circuit current densities that were calculated using these lifetimes agreed reasonably well with measured values for bifacial dendritic web silicon solar cells. The measurements were made over a range of doping densities (6*10/sup 14/ to 3*10/sup 16/ cm/sup -3/) and illumination levels (0.001 to 1 sun) for both front and back illumination of the bifacial cells. >

In ionizing-radiation environments, oxide charge buildup in the buried oxide of SIMOX SOI material causes an increase in the back-channel leakage current, resulting in an instability in electronic circuits formed on SIMOX wafers. We report the measured distributions of radiation-induced oxide charge density in buried oxides formed by oxygen implantation. These are obtained by etch-back experiments including C-V measurements using a mercury probe and ellipsometer measurements. The results show a region of higher charge density about 1500A from the top interface with a lower density region within a few hundred angstroms of the top interface. The results also show that the oxide charge density decreases with annealing temperature. Some unusual optical properties of SIMOX oxide observed in ellipsometer measurements are discussed comparatively with thermal oxide.