Gary E. Carver

Photoluminescence imaging of porous silicon using a confocal scanning laser macroscope/microscope

This letter describes a confocal scanning beam macroscope/microscope that can image specimens up to 7 cm in diameter using both photoluminescence and reflected light. The macroscope generates digital images (512×512 pixels) with a maximum 5 μm lateral resolution and 200 μm axial resolution in under 5 s, and in combination with a conventional confocal scanning laser microscope can provide quality control at a macroscopic/microscopic level for porous silicon specimens, wafers, detectors, and similar devices. This combination of instruments can also be used as a method for evaluating preparation parameters involved in the manufacture of porous silicon. Various confocal and nonconfocal photoluminescence and reflected‐light images of porous silicon are shown using both a macroscope and a conventional confocal scanning laser microscope. A 3D profile of a porous silicon structure reconstructed from confocal slices is also shown.

Comparative Study of Light-Emitting Porous Silicon Anodized with Light Assistance and in the Dark

In this study, we compare two different types of light emitting porous silicon (LEpSi) samples: LEpSi anodized in the dark (DA) and LEpSi anodized with light assistance (LA). On the basis of photoluminescence (PL), Raman, FTIR, SEM, spatially resolved reflectance (SRR) and spatially resolved photoluminescence (SRPL) studies, we demonstrate that the luminescence in LA porous silicon is strong, easily tunable, very stable and originates from macropore areas. These attractive properties result from passivation by oxygen in the Si-O-Si bridging configuration that takes place during electrochemical anodization. In addition, we have been able to correlate light emission with the presence of crystalline silicon nanograins.

Prospects for light-emitting diodes made of porous silicon from the blue to beyond 1.5 μm

Since the 1990 discovery that porous silicon emits bright photoluminescence in the red part of the spectrum, light-emitting devices (LEDs) made of light-emitting porous silicon (LEPSi) have been demonstrated, which could be used for optical displays, sensors or optical interconnects. In this paper, we discuss our work on the optical properties of LEPSi and progress towards commercial devices. LEPSi photoluminesces not only in the red- orange, but also throughout the entire visible spectrum, from the blue to the deep red, and in the infrared, well past 1.5 micrometers . The intense blue and infrared emissions are possible only after treatments such as high temperature oxidation or low temperature vacuum annealing. These new bands have quite different properties form the usual red-orange band and their possible origins are discussed. Different LED structures are then presented and compared and the prospects for commercial devices are examined.

Wafer level testing for semiconductor laser manufacture via spatially resolved photoluminescence

High bandwidth telecommunications depends on the efficient manufacture of semiconductor lasers. The quality of partially processed laser structures can be monitored at the wafer level by spatially resolved photoluminescence (SRPL), providing timely feedback to processing engineers. The same testing procedure can also be applied at the chip level. This allows comparisons of wafer level material quality, chip level material quality, and chip performance.

Mapping of electrically active defects in silicon by optical-beam-induced reflectance

Abstract The mapping of electrically active defects in silicon is of interest in the semiconductor industry. Non-destructive approaches with high spatial resolution allow material to be screened for micro-defects, and then submitted for processing. The non-contact optical beam-induced reflectance (OBIR) technique employs a pump/probe laser configuration to reveal micrometer sized, electrically active features near the surface of silicon wafers. The system combines the spatial resolution possible with visible light with the sensitivity to carrier concentration exhibited by IR radiation. This paper presents a two-dimensional model of the photoexcited carrier and temperature distributions. The results indicate that the OBIR signal is dominated by carrier density, and that carrier diffusion does not prevent high spatial resolution. Spatial scans exhibiting metallic precipitates and epitaxial stacking faults are also presented.

SRPL mapping of semiconductor laser wafers

High bandwidth telecommunications depends on the efficient manufacture of semiconductor lasers. The quality of partially processed laser structures can be monitored at the wafer level by spatially resolved photoluminescence (SRPL), providing timely feedback to processing engineers.