Mid-infrared (MIR) silicon photonics holds the potential for realizing next generation ultra-compact spectroscopic systems for applications in gas sensing, defense and medical diagnostics. The direct epitaxial growth of antimonide-based compound semiconductors on silicon provides a promising approach for extending the wavelength of silicon photonics to the longer infrared range. This paper reports on the fabrication of a high performance MIR photodetector directly grown onto silicon by molecular beam epitaxy. The device exhibited an extended cut-off wavelength at ~5.5 μm and a dark current density of 1.4 x 10^-2 A/cm² under 100 mV reverse bias at 200 K. A responsivity of 0.88 A/W and a specific detectivity in the order of 1.5 x 10¹⁰ Jones was measured at 200 K under 100 mV reverse bias operation. These results were achieved through the development of an innovative structure which incorporates a type-II InAs/InAsSb superlattice-based barrier nBn photodetector grown on a GaSb-on-Silicon buffer layer. The difficulties in growing GaSb directly on silicon were overcome using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step growth temperature procedure and dislocation filters resulting in a low defect density, anti-phase domain free GaSb epitaxial layer on silicon. This work demonstrates that complex superlattice-based MIR photodetectors can be directly integrated onto a Si platform, which provides a pathway towards the realization of new, high performance, large area focal plane arrays and mid-infrared integrated photonic circuits.

Avalanche multiplication and excess noise arising from both electron and hole injection have been measured on a series of In_0.52Al_0.48As p⁺-i-n⁺ and n ⁺-i-p⁺ diodes with nominal avalanche region widths between 0.1 and 2.5 mum. With pure electron injection, low excess noise was measured at values corresponding to effective k=beta/alpha between 0.15 and 0.25 for all widths. Enabled ionization coefficients were deduced using a non-local ionization model utilizing recurrence equation techniques covering an electric field range from approximately 200 kV/cm to 1 MV/cm

InAs thermophotovoltaic (TPV) cells with external quantum efficiency at the peak wavelengths reaching 71% at low temperature and 55% at room temperature are reported, which are the highest values to date for InAs. The TPV exhibited 10% power conversion efficiency at 100 K cell temperature. The dark and light current-voltage characteristics were measured at different cell temperatures (100–340 K) in response to heat sources in the range 500–800 °C. The resulting dependences of the output voltage and current as well as the spectral response of the InAs TPV have been extensively characterized for waste heat recovery applications. The performance of these cells is strongly determined by the dark current which increases rapidly with increasing cell temperature originating from bandgap narrowing, which resulted in a reduction of open circuit voltage and output power

A systematic study of avalanche multiplication on a series of In _0.52Al_0.48As p⁺-i-n⁺ and n ⁺-i-p⁺ diodes with nominal intrinsic region thicknesses ranging from 0.1 to 2.5 mum has been used to deduce effective ionization coefficients between 220 and 980 kVmiddotcm^-1. The electron and hole ionization coefficient ratio varies from 32.6 to 1.2 with increasing field. Tunneling begins to dominate the bulk current prior to avalanche breakdown in the 0.1-mum-thick structure, imposing an upper limit to the operating field. While the local model can accurately predict the breakdown in the diodes, multiplication is overestimated at low fields. The effects of ionization dead space, which becomes more significant as the intrinsic region thickness reduces, can be corrected for by using a simple correction technique

Axially doped p-i-n InAs0.93Sb0.07 nanowire arrays have been grown on Si substrates and fabricated into photodetectors for shortwave infrared detection. The devices exhibit a leakage current density around 2 mA/cm2 and a 20% cut-off of 2.3 μm at 300 K. This record low leakage current density for InAsSb devices demonstrates the suitability of nanowires for the integration of III-V semiconductors with silicon technology.

An experimental investigation into impact ionization in InAs photodiodes is presented. Photomultiplication measurements on p-i-n and n-i-p diodes show that while high avalanche gains can be obtained for electron initiated multiplication, there is virtually no gain with hole initiated multiplication. This indicates that the electron ionization coefficient is significantly greater than the hole ionization coefficient raising the possibility of extremely low noise InAs avalanche photodiodes when gain is initiated by electrons. The onset of electron initiated impact ionization was detectable at electric fields below 10kVcm−1 with useful gain observed at biases below 10V.