Peak Detection Wavelength Research Articles

Investigation of a multistack voltage-tunable four-color quantum-well infrared photodetector for mid- and long-wavelength infrared detection

A four-color quantum-well infrared photodetector (QWIP) for mid- and long-wavelength infrared (MWIR and LWIR) detection has been demonstrated in this work. Four stacks of QW structures with four different detection wavelengths are sandwiched between three highly doped contact layers. Peak detection wavelengths of this device are centered at 4.7, 8.5, 9, and 12.3 /spl mu/m, respectively. The 4.7- and 8.5-/spl mu/m stacks are separated from the 9- and 12.3-/spl mu/m stacks by a middle contact layer, and the peak detection wavelength within these two double-stack QWIP's can be tuned by the applied bias. Four different combinations of two-color simultaneous readings can be achieved. By using a small number of QW's and balancing the impedance between the stacks, we are able to use all four stacks for voltage-tunable multicolor detection with two terminals. The bias and temperature dependence of the dark current and peak responsivity as well as the dynamic impedance in this four-color QWIP were systematically studied over a wide range of bias and temperature. In spite of using four different stacks of strained InGaAs-AlGaAs and GaAs-AlGaAs materials, the device shows excellent material quality and performance.

A normal incidence p-type strain layer quantum well infrared photodetector with 19.2 μm peak detection wavelength

A normal incidence p-type compressively strained layer superlattice (SL) In0.27Ga0.73As/Al0.15Ga0.85As quantum well infrared photodetector with a spectral response peak at 19.2 μm and a cutoff wavelength λc>20 μm under moderate background illumination have been demonstrated in this work. A responsivity of 50 mA/W and a gain-quantum efficiency product (ηg) of 0.32% at Vb=20 mV and T=40 K were obtained for this device. The device layer structure consists of four InGaAs/AlGaAs SL-absorber layers sandwiched by wide GaAs barrier layers. Results of the responsivity, dark current, noise, background photocurrent measurements, and analysis of the device performance are discussed.

A two-stack indirect-barrier/triple-coupled quantum well infrared detector for mid-wavelength and long-wavelength infrared dual band detection

We report a two-stack indirect-barrier (IB) GaAs/AlGaAs quantum well infrared photodetector (QWIP) for mid-wavelength infrared (MWIR) and a voltage-tunable InGaAs/GaAs/AlGaAs triple-coupled (TC) QWIP for long-wavelength infrared (LWIR) detection. The peak responsivity of the stacked QWIP at zero bias (PV mode) was found to be 30 mA/W at λp=4.3μm and T=40 K. The maximum peak responsivity for the stacked QWIP was found to be 0.21 A/W at λp=4.3 μm, Vb=4 V, and T=40 K. For the LWIR TC-QWIP, the peak detection wavelength due to (E1→E3) transition shifts from 10 to 9.4 μm as bias voltage increases from 7 to 12 V. The maximum responsivity was found to be 0.085 A/W at λp=9.4 μm, Vb=12 V, and T=40 K. The results show that simultaneously detection of both the MWIR and LWIR bands can be achieved at Vb⩾7 V or Vb⩽−5 V. It is shown that this two-stack QWIP can be used as a voltage-tunable two-color or multicolor QWIP for the MWIR and LWIR dual band detection.

Aluminum free GaInP/GaAs quantum well infrared photodetectors for long wavelength detection

We demonstrate quantum well infrared photodetectors based on a GaAs/Ga0.51In0.49P superlattice structure grown by gas-source molecular beam epitaxy. Wafers were grown with varying well widths. Wells of 40, 65, and 75 Å resulted in peak detection wavelengths of 10.4, 12.8, and 13.3 μm with a cutoff wavelength of 13.5, 15, and 15.5 μm, respectively. The measured peak and cutoff wavelengths match those predicted by eight band theoretical analysis. Measured dark currents were lower than equivalent GaAs/AlGaAs samples.

Effect of interdiffusion of quantum well infrared photodetector

The intersubband infrared photodetector performance is theoretically analyzed for various stages of interdiffusion in AlGaAs/GaAs quantum well. The absorption strength and responsivity are enhanced for certain extents of interdiffusion and the peak detection wavelength red shifts continuously with a large tunable range from 7 to 38.4 μm. The dark current is at an acceptable value for small diffusion extent.

An asymmetric quantum well infrared photodetector with voltage-tunable narrow and broad-band response

We describe a 9 μm AlGaAs/GaAs asymmetric quantum well infrared photodetector with voltage tunable spectral bandwidth. A very narrow spectral response of 9.2 meV (0.6 μm) full width half maximum is observed for an applied electric field of 28 kV/cm. The linewidth quadruples when the bias polarity is reversed, with very little shift in the peak detection wavelength. This structure is based on a conventional intersubband photodetector modified by using AlGaAs barriers that are graded in Al content and by adding a thin AlGaAs confinement layer on one side of the well. The asymmetry in the barriers is shown to give rise to the dependence of the spectral linewidth on applied bias. As well, a series of unusually well-resolved and intense bound-to-continuum transitions are observed at low bias, that may indicate that the unique barrier shape also leads to enhanced electron interference effects at the well/barrier interfaces.

Postgrowth tuning of quantum-well infrared detectors by rapid thermal annealing

The peak detection wavelength of an operational quantum-well infrared photodetector structure has been red shifted using rapid thermal annealing to partially intermix the well and barrier layers. Successive anneals at 850 °C were used to tune an 8.13 μm detector continuously out to 9.13 μm. All of the fabricated detectors were operational in spite of very long annealing times of up to 300 s. The peak spectral responsivity at a device current of 10 μA dropped from 0.62 to 0.12 A/W after the longest anneal time, but the broadband responsivity only dropped by a factor of 3 due to a simultaneous increase in the detection spectral bandwidth.