Abstract
Near infrared light detection is fundamental for sensing in various application fields. In this paper, we detail the properties of InGaAs/AlGaAs multiple quantum well (MQW) photodetectors (PDs) monolithically integrated by direct epitaxy on 300 mm Si(001) substrates. A MQW high crystalline quality is achieved using 300 mm Ge/Si pseudo-substrates with a low threading dislocation density of 4 × 107 cm−2 from electron channeling contrast imaging measurements. The localized states in the MQW stack are investigated using temperature-dependent photoluminescence. Two non-radiative recombination channels are identified. The first one is due to delocalized excitons generated by potential’s fluctuations because of the InGaAs/AlGaAs interfacial roughness (with an activation energy below 4 meV). The second one is due to exciton quenching because of the presence of numerous threading dislocations. A low dark current density of 2.5 × 10−5 A/cm2 is measured for PDs on Ge/Si substrates, i.e., a value very close to that of the same PDs grown directly on GaAs(001) substrates. A responsivity of 36 mA/W is otherwise measured for the photodiode on Ge/Si at room temperature and at −2 V.
Highlights
INTRODUCTIONQuantum well infrared photodetectors (QWIPs) have been extensively developed since the first observation of infrared transition (intersubband transition) in a GaAs QW embedded between two Al0.3Ga0.7As barrier layers. QWIPs with InxGa1−xAs multiple quantum wells (MQWs) as active regions have a potential for midwave infrared (MWIR; 3 up to 5 μm band) and long-wave infrared (LWIR; 8 up to 12 μm band) detection
Quantum well infrared photodetectors (QWIPs) with InxGa1−xAs multiple quantum wells (MQWs) as active regions have a potential for midwave infrared (MWIR; 3 up to 5 μm band) and long-wave infrared (LWIR; 8 up to 12 μm band) detection
GaAs layers were grown in two steps: 40 nm thick nucleation layers were deposited at low temperatures (LT, 400–500 ○C) followed by the growth of 370 nm thick GaAs layers at high temperatures (HT, 600–700 ○C).27 n-type doping was achieved with disilane as the n-type precursor, with a molecular flow of 1 μmol/min of Si resulting in a doping level of 2 × 1018 cm−3
Summary
Quantum well infrared photodetectors (QWIPs) have been extensively developed since the first observation of infrared transition (intersubband transition) in a GaAs QW embedded between two Al0.3Ga0.7As barrier layers. QWIPs with InxGa1−xAs multiple quantum wells (MQWs) as active regions have a potential for midwave infrared (MWIR; 3 up to 5 μm band) and long-wave infrared (LWIR; 8 up to 12 μm band) detection. QWIPs with InxGa1−xAs multiple quantum wells (MQWs) as active regions have a potential for midwave infrared (MWIR; 3 up to 5 μm band) and long-wave infrared (LWIR; 8 up to 12 μm band) detection. They are suitable for military and civilian applications in night vision cameras, thermal imaging systems, and medical imaging (neuroimaging, cancer detection, etc.). Katzer et al. have investigated InGaAs/AlGaAs vertical PIN MQW optical modulators They showed that indium concentrations less than 23% in those MQWs grown directly on GaAs resulted in better device performances than those with higher indium concentrations. Our results show how the MQW quality affects the device operation and the potential of our approach to fabricate efficient PDs at large scales
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