Strain-induced modifications of the band structure of InxGa1-xP–In0.5Al0.5P multiple quantum wells

Includes bibliographical references.The effect of strain on the band structure of InxGa1-xP-In0.5Al0.5P multiple quantum wells (MQW's) has been investigated from high-pressure and low-temperature photoluminescence measurements. The biaxial strain in the wells was varied between +0.6% compressive to -0.85% tensile strain by changing the well composition x from 0.57 to 0.37. Strain increases the valence band offsets in either tensile or compressively strained structures. Whereas relatively insensitive to tensile strain, the valence band offsets showed a strong dependence on the magnitude of the compressive strain. Good agreement is found between the measured valence band offsets and those predicted by the model solid theory, except for the largest compressively strained MQW's, for which the model calculations underestimate the measured valence band offset. Strain and the associated variations in composition also modified the separation among the well states associated with Γ1c, L1c, and X1c. From these results, the bandgaps of each conduction band extrema were calculated in InxGa1-xP for 0.37 < x < 0.57 and compared with the predictions of the model solid theory.This work was supported by the National Science Foundation under Grant DMR 9321422 and Grant ECS-9502888, and by the AFOSR under Contract F49620-93-1-0021

Effect of indirect Γ-L and Γ-X transfer on the carrier dynamics of InGaP/InAlP multiple quantum wells

Includes bibliographical references (page 104).Indirect Γ-L scattering within the well, and real space carrier transfer to the barrier X1c states are shown to significantly affect the carrier dynamics in In0.48Ga0.52P/In0.5Al0.5P multiple quantum wells. When carriers transfer to the indirect states occurs, the carrier dynamics is modified by the slow return of the carriers from the low mobility states to the well. As a result, the absorption recovery time increases by almost an order of magnitude. Carrier transfer to the indirect states also increases the carrier lifetime to values characteristic of indirect recombination.This work is supported by the National Science Foundation through Grant Nos. DMR 9321422, ECS-9502888, EEC-9015128, the Colorado Advanced Technology Institute, Grant No. 0594.75.0738, and by AFOSR contract F49620-93-1-0021

A systematic review of the drug-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Indian population

Background: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare severe cutaneous drug reactions. No large scale epidemiological data are available for this disorder in India. Aims: To carry out a systematic review of the published evidence of the drug-induced SJS and TEN in Indian population. Methods: Publications from 1995 to 2011 describing SJS and TEN in Indian population were searched in PubMed, MEDLINE, EMBASE and UK PUBMED Central electronic databases. Data were collected for the causative drugs and other clinical characteristics of SJS and TEN from the selected studies.Results: From 225 references, 10 references were included as per selection criteria. The major causative drugs were antimicrobials (37.27%), anti-epileptics (35.73%) and non-steroidal anti-inflammatory drugs (15.93%). Carbamazepine (18.25%), phenytoin (13.37%), fluoroquinolones (8.48%) and paracetamol (6.17%) were most commonly implicated drugs. Regional differences were observed for fluoroquinolones, sulfa drugs and carbamazepine. Total 62.96% of patients showed systemic complications. Most common complications were ocular (40.29%) and septicemia (17.65%). Higher mortality was observed for TEN as compared to SJS (odd ratio-7.19; 95% confidence interval (CI) 1.62-31.92; p = 0.0023). Observed mortality is higher than expected as per SCORTEN score 3. Duration of hospital stay was significantly higher in TEN (20.6 days; 95% CI 14.4-26.8) as compared to SJS (9.7 days; 95% CI 5.8-13.6; p = 0.020). Cost of management was significantly higher in TEN (Rs. 7910; 95% CI 5672-10147; p < 0.0001) as compared to SJS (Rs 2460; 95% CI 1762-3158). No statistical data were described for steroid use in the studies included. Conclusion: Carbamazepine, phenytoin, fluoroquinolones and paracetamol were the major causative drugs. TEN is showing higher mortality, morbidity and economic burden than SJS

Nonlinear macroscopic polarization in GaN/AlxGa1-xN quantum wells

Includes bibliographical references (page 4213).We present experimental evidence of the nonlinear behavior of the macroscopic polarization in GaN/AlxGa1-xN quantum wells. This behavior is revealed by determining the barrier-well polarization difference as a function of applied hydrostatic pressure. The polarization difference and corresponding built-in electric field in the wells increase with applied pressure at a much higher rate than expected from the linear model of polarization. This result, universally observed in the quantum well structures with different AlN mole fraction in the barriers, is explained by the nonlinear dependence of the piezoelectric polarization in GaN and AlN on the strain generated by pressure