Progress in Symmetric and Asymmetric Superlattice Quantum Well Infrared Photodetectors

Abstract

Herein, two challenges are addressed, which quantum well infrared photodetectors (QWIPs), based on III-V semiconductors, face, namely: photodetection within the so-called "forbidden gap", between 1.7 and 2.5 microns, and room temperature operation using thermal sources. First, to reach this forbidden wavelength range, a QWIP which consists of a superlattice structure with a central quantum well (QW) with a different thickness is presented. The different QW in the symmetric structure, which plays the role of a defect in the otherwise periodic structure, gives rise to localized states in the continuum. The proposed InGaAs/InAlAs superlattice QWIP detects radiation around 2.1 microns, beyond the materials bandoffset. Additionally, the wavefunction parity anomaly is explored to increase the oscillator strength of the optical transitions involving higher order states. Second, with the purpose of achieving room temperature operation, an asymmetric InGaAs/InAlAs superlattice, in which the QW with a different thickness is not in the center, is used to detect infrared radiation around 4 microns at 300 K. This structure operates in the photovoltaic mode because it gives rise to states in the continuum which are localized in one direction and extended in the other, leading to a preferential direction for current flow.

Electronic Confinement in the Continuum: Leaky Bragg Mirror for Electrons

“…Both QWIPs and QCDs depend on the electronic confinement and the energy levels that result from this confinement. In order to create another degree of freedom to tune the energy levels, photodetectors based on localized electronic states in the continuum were developed [5][6][7][8][9].…”

Role of Structural Parameters on the Leaky Electronic States in the Continuum of Superlattice Structures

“…Such state does not present any leaky path to the continuum (nonradiative state) [1,2]. Recently, the BICs have been extensively explored in diverse systems, such as photonics [3], metamaterials [4], THz resonators [5], and superlattice infrared photodetectors (SLIPs) [6]. In particular, their use in InGaAs/InAlAs SLIPs presents many advantages over the quantum well infrared photodetectors (QWIPs), which are: low thermal excitation, anomalous parity, detection energy not limited by the material band offset, dual-mode operation, and room temperature operation [7][8][9][10][11].…”

Projeto, Construção e Controle de um Chopper Óptico operando na faixa de 100Hz-300Hz

“…O Chopperópticoé um instrumento científico utilizado com a finalidade de modular a intensidade de um feixe de luz, o queé feito interrompendo a luz periodicamente através de um disco dentado. Tal equipamentoé extremamente importante para investigação das propriedades elétricas é opticas de materiais semicondutores nanoestruturados e de dispositivos optoeletrônicos(M. Penello et al (2019)). Para seu perfeito funcionamento,é necessário que o disco dentado se mantenha girando em uma frequência fixa especificada por seu utilizador.…”