We show that the emission characteristics of InGaN/GaN quantum wells under hydrostatic pressure are strongly influenced by the built-in piezoelectric field. The dominant role of the piezoelectric field is established from the dramatic increase of the photoluminescence decay time with pressure and the dependence of the linear pressure coefficient of the photoluminescence peak energy on Si doping in the barriers and excitation intensity. A nonlinear increase of the piezoelectric field with hydrostatic pressure determined from these experiments is explained as being due to a significant dependence of the InGaN piezoelectric constants with strain.

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Images with a spatial resolution of 120-150 nm were obtained with 46.9 nm light from a compact capillarydischarge laser by use of the combination of a Sc-Si multilayer-coated Schwarzschild condenser and a freestanding imaging zone plate. The results are relevant to the development of compact extreme-ultraviolet laser-based imaging tools for nanoscience and nanotechnology. © 2005 Optical Society of America OCIS codes: 180.7460, 110.7440, 140.7240. Rapid progress in nanotechnology and nanoscience creates the need for new practical imaging tools capable of resolving nanometer-sized features. Shortwavelength light provides an opportunity to develop optical imaging systems with the highest resolution. The best resolution so far, 20 nm, has been obtained in imaging with soft-x-ray synchrotron radiation at 2.07 nm wavelength. 1 Submicrometer resolution was obtained with a soft-x-ray recombination laser, 2 and 75 nm resolution was reported with a low-repetitionrate (several pulses per day) laboratory-sized soft-xray laser.3 There is, however, a need for the development of more compact and practical nanometerresolution imaging systems. Toward this goal extreme-ultraviolet (EUV) light from high-order harmonic sources was used to demonstrate imaging systems with a resolution of better than 1 m, 4,5 and soft-x-ray imaging with laser-plasma-based sources has been investigated. [6][7][8] In this Letter we report what is to our knowledge the first demonstration of nanometer-scale imaging with a compact capillary-discharge pumped highrepetition-rate EUV laser. Spatial resolution of the 46.9 nm wavelength system is estimated to be 120-150 nm. This is to our knowledge the highest resolution achieved with a compact high-repetitionrate coherent EUV illumination source. The high average power ͑ϳ1 mW͒ and multihertz repetition rate of the Ne-like Ar capillary discharge laser source that we used 9,10 allowed us to perform real-time imaging, for which the image is continuously updated on the computer screen at the rate of the laser pulses.The imaging system is schematically illustrated in Fig. 1. It consists of a compact capillary-discharge 46.9 nm laser, a Sc-Si multilayer-coated reflective condenser, a zone-plate objective, and a CCD detector. The condenser, the imaged sample, and the objective were mounted onto motorized translation stages that were assembled inside a vacuum chamber connected to the EUV laser source with standard vacuum fittings. The illumination source is a compact capillary-discharge Ne-like Ar laser emitting at a wavelength of 46.9 nm with a pulse duration of ϳ1.2 ns. Its short wavelength, narrow spectral bandwidth, high photon fluence, and beam directionality make this source well suited for microscopy. The spectral bandwidth of the laser is ⌬ / Ͻ10 −4 . 9 The laser's output pulse energy and degree of spatial coherence depend on the capillary discharge length. For this experiment the laser was equipped with an 18 cm capillary discharge tube that provided an average pulse energy of ϳ0.1 mJ. This choice of cap...

Abstract-We present a novel analysis for correcting the measured differential carrier lifetime to account for carrier population in both the barrier and separate confinement heterostructure (SCH) regions of quantum-well (QW) lasers. This analysis uses information obtained from the measured spontaneous emission spectra to correct the measured lifetime and obtain the intrinsic well lifetime. Once the intrinsic well lifetime is obtained, the intrinsic well recombination coefficients can also be obtained. We show that the carrier population in the barrier/SCH layers can significantly affect the measured carrier lifetime and the extracted recombination coefficients. We also show that this analysis yields transparency carrier density and differential gain numbers which are very different from those obtained with the traditional analysis and much closer to what is predicted for highly strained QW lasers. These differences indicate the importance of accounting for barrier/SCH carriers on the measurement of basic QW laser material properties.