Abstract. We report the critical factors that control the geometry of silicon nanostructures produced by metalassisted chemical etching (MacEtch) using self-assembled islands from an ultrathin film of gold. We have conducted a systematic study of the process parameters that control the geometry of the metal structures and the resulting etched nanostructures. Compared to prior reports, which have focused on the crystal orientation and solution stoichiometry, our study finds that the anisotropy of the etched nanostructures is primarily controlled by the deposited metal geometry, while solution stoichiometry and crystal orientation play relatively minor roles.Using an optimized self-assembled geometry and etch process, we demonstrate what we believe is the highest aspect ratio to date (greater than 5000∶1) for high density top-down etched silicon nanostructures. These structures, which we refer to as silicon nanowalls, are in the size regime where quantum confinement effects could potentially be exploited for next-generation optoelectronic components and devices. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

This paper reports an InAs/InAsSb strained-layer superlattice (SLS) mid-wavelength infrared detector and a focal plane array particularly suited for high-temperature operation. Utilizing the nBn architecture, the detector structure was grown by molecular beam epitaxy and consists of a 5.5 µm thick n-type SLS as the infrared-absorbing element. Through detailed characterization, it was found that the detector exhibits a cut-off wavelength of 5.5 um, a peak external quantum efficiency (without anti-reflection coating) of 56%, and a dark current of 3.4 × 10−4 A/cm2, which is a factor of 9 times Rule 07, at 160 K temperature. It was also found that the quantum efficiency increases with temperature and reaches ~56% at 140 K, which is probably due to the diffusion length being shorter than the absorber thickness at temperatures below 140 K. A 320 × 256 focal plane array was also fabricated and tested, revealing noise equivalent temperature difference of ~10 mK at 80 K with f/2.3 optics and 3 ms integration time. The overall performance indicates that these SLS detectors have the potential to reach the performance comparable to InSb detectors at temperatures higher than 80 K, enabling high-temperature operation.

The objective of this paper is to provide a credible analysis for predicting the spectral responsivity of InAs/GaSb/AlSb type-II superlattice (T2SL) based dual-band infrared photodetectors. An overview of the T2SL based design criteria is given and new dual-band detector architecture with a model dual-band detector structure designed to detect light in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) ranges is presented. The absorption coefficient is modeled empirically and the quantum efficiency spectra are calculated using a numerical model and Hovel’s analytical expressions. The spectral cross-talk due to the response of the LWIR channel to residual MWIR light is also investigated. It is shown that the significance of this cross-talk primarily depends on the temperature of the target (scene) being detected. For MWIR/MWIR (two bands in the MWIR range) dual-band detectors, the spectral cross-talk becomes significant irrespective of the target temperature. Eliminating the spectral cross-talk in T2SL dual-band detectors presently remains a challenge.

We observed up to 100 times enhancement of sensitivity of mid-wave infrared photodetectors in the 2–5 μm range by using photonic jets produced by sapphire, polystyrene, and soda-lime glass microspheres with diameters in the 90–300 μm range. By finite-difference time-domain (FDTD) method for modeling, we gain insight into the role of the microspheres refractive index, size, and alignment with respect to the detector mesa. A combination of enhanced sensitivity with angle-of-view (AOV) up to 20° is demonstrated for individual photodetectors. It is proposed that integration with microspheres can be scaled up for large focal plane arrays, which should provide maximal light collection efficiencies with wide AOVs, a combination of properties highly attractive for imaging applications.