J.-L. Lazzari

InAsN/GaSb/InAsN 'W' quantum well laser for mid-infrared emission: from electronic structure to threshold current density calculations

The electronic band-structure and optical gain properties of dilute-nitride InAsN/GaSb/InAsN type-II W quantum wells based mid-infrared laser diodes on InAs substrate are numerically investigated with an accurate 10-bands kp model. The laser diodes are designed to operate at 3.3??m at room temperature. The dispersion relations, the optical gain and the threshold current density including computation of non-radiative Auger recombination rate are calculated. For typical injected carrier concentration of 1.5 ? 1018?cm?3 at 300?K, peak gain values of the order of 1000?cm?1 are reached and a modal gain value equal to 70?cm?1 can be achieved. By evaluating reasonable optical losses, a threshold current density around 500?A?cm?2 is expected, showing that dilute-nitride InAsN/GaSb/InAsN W quantum wells are suitable for mid-infrared laser operation at room temperature.

A theoretical study of laser structures based on dilute-nitride InAsN for mid-infrared operation

New dilute-nitride InAsN/GaSb laser diodes on an InAs substrate with a W or M design are theoretically investigated using a ten-band k ⋅ p model including valence, conduction and nitrogen-induced bands. For these laser diodes, designed to operate at 3.3 µm at room temperature, optical transition matrix elements for TE and TM modes between the valence sub-bands and the conduction sub-bands, modal gain and total threshold current densities are calculated. Under the hypothesis of a total loss coefficient α = 50 cm−1, non-conventional W and M multiquantum well laser structures present a calculated threshold current density Jth lower than 1.1 kA cm−2.

Electronic and magnetic properties of Mn-doped BeSiAs2 and BeGeAs2 compounds

The structural, electronic and magnetic properties of BeSiAs(2) and BeGeAs(2) chalcopyrite ternary compounds doped with manganese were investigated by means of ab initio calculations. It was found that substitution of Be atoms by Mn increases the lattice constants of both compounds that provide acceptable mismatch with conventional Si, Ge and GaAs substrates. Inxa0spite of the increase of the spin polarization upon doping, both compounds possess antiferromagnetic (AFM) ordering with the impurity in the group II position whereas ferromagnetic (FM) ordering is obtained in the case of an impurity in the group IV position.

A multi-color quantum well photodetector for mid- and long-wavelength infrared detection

The authors report a two-color quantum well infrared photodetector at room temperature operating in the mid- and long-wavelength infrared detection. To this purpose, the band alignment is tailored and electronic properties are investigated for the proposed structure based on Ga1−xInxAsySb1−y/GaSb and AlxGa1−xAsySb1−y/GaSb. As accurate knowledge of band offsets is required in device modeling, we have proceeded to theoretical investigations of the band offsets for pseudo-morphically strained and lattice-matched Ga1−xInxAsySb1−y/GaSb and AlxGa1−xAsySb1−y/GaSb heterointerfaces in the whole range of alloy compositions 0 ≤ x, y ≤ 1. The carrier effective masses are deduced from the laws extracted from the k.p strain Hamiltonian laws. For the modeled heterostructure, the dark current of about 10−1 A cm−2 at ambient temperature shows the high performance of this multi-color infrared photodetector around 5 and 12.5 µm wavelengths.

Performance evaluation of high-detectivity p-i-n infrared photodetector based on compressively-strained Ge0.964Sn0.036/Ge multiple quantum wells by quantum modelling

GeSn/Ge p-i-n photodetectors with practical Ge0.964Sn0.036 active layers are theoretically investigated. First, we calculated the electronic band parameters for the heterointerfaces between strained Ge1−xSnx and relaxed (001)-oriented Ge. The carrier transport in a p-i-n photodiode built on a ten-period Ge0.964Sn0.036/Ge multiple quantum well absorber was then analyzed and numerically simulated within the Tsu−Esaki formalism by self-consistently solving the Schrodinger and Poisson equations, coupled to the kinetic rate equations. Photodetection up to a 2.1 μm cut-off wavelength is achieved. High responsivities of 0.62 A W−1 and 0.71 A W−1 were obtained under a reverse bias voltage of −3 V at peak wavelengths of 1550 nm and 1781 nm, respectively. Even for this low Sn-fraction, it is found that the photodetector quantum efficiency (49%@1.55 μm) is higher than those of comparable pure-Ge devices at room temperature. Detectivity of 3.8 × 1010 cm Hz1/2 W−1 and 7.9 × 1010 cm Hz1/2 W−1 at −1 V and −0.5 V, respectively, is achievable at room temperature for a 1550 nm wavelength peak of responsivity. This work represents a step forward in developing GeSn/Ge based infrared photodetectors.

Resonant tunneling transport in Al z Ga1−z N/In x Ga1−x N/Al z Ga1−z N/In y Ga1−y N quantum structures

We present a room temperature simulation of the vertical electron transport in the pseudomorphic quantum stack Al0.5G0.5N/In x Ga1−x N/Al0.5G0.5N/In0.1Ga0.9N/GaN, which is designed with a 6 nm thick lateral In0.1Ga0.9N/GaN n-type corrected spacer. Using the transfer matrix formalism, we investigate the effects of the conduction band discontinuities and internal field on the transmission coefficient and the current-voltage characteristics by varying the indium contents in the central quantum well. We demonstrate that an optimal design in terms of compositions, thicknesses, and doping of the studied resonant tunneling structure may allow a peak-to-valley ratio as high as 882 @1.1–1.3 V.

Engineering of Ga1−xInxAsySb1−y/GaSb quantum well for III-V based devices emitting near 2.7 μm

The present investigation is focused on the electronic band parameters for Ga1−xInxAsySb1−y/GaSb quantum wells. Strain effects on heavy holes (hh), light holes (lh) and split off (so) bands are investigated as a function of indium and arsenic compositions in the hole range 0 ≤ x, y ≤ 1. The valence band offsets are calculated using the model solid theory. Taking into account these results and based on a one dimensional Schrodinger equation, we report a calculation of the quantum confinement of electron and heavy-hole levels for Ga1−xInxAsySb1−y/GaSb quantum well (QW). Our results provide useful information for the design of heterostructure emitting near 2.7 μm.