Investigation of a novel multicolor quantum well infrared photodetector and advanced quantum dot infrared photodetectors

In this work, a novel three-stack three-color quantum well infrared photodetector (QWIP) and five quantum dot infrared photodetectors (QDIPs) have been developed. The QWIP is designed to cover three blocking bands in the 3∼16 mum atmospheric spectral window. The QDIP designs are focused on realizing the predicted benefits which include normal incident detection, low dark current, high operation temperature, and possible multi-color applications. The detection wavelengths of QDIPs cover from 3∼20 mum waveband.; The 3-stack, 3-color QWIP cover the detection in the H2O, O3, and CO2 atmosphere spectral blocking bands. The bottom QWIP stack (H2O band) is formed by using AlGaAs/InGaAs graded barrier with thin AlGaAs double-barrier in the InGaAs quantum well and the bound-to-bound (B-B) transition. The middle stack (O3 band) is fabricated by using AlGaAs/InGaAs quantum well and the bound-to-quasi-bound (B-QB) transition. The top stack is formed by using AlGaAs/InGaAs graded barrier and the B-B transition for infrared detection. The full-width half-maximum (FWHM) of the top, middle and bottom stacks is 5.9∼7.0 mum, 9.1∼11.2 mum, and 12.2∼16.9 mum, respectively. The peak detectivity values are varied from 1010 to 1012 cm-Hz1/2/W at T = 30K∼40K for the three QWIP stacks.; The first QDIP device is composed of a 10-period 2.7-monolayer (ML) InAs QD/400 A GaAs spacer with a 40 A In0.5Ga0.5P blocking layer in each stack. The major detection wave band covers from 9.8mum to 13.5mum. The normal incident responsivity up to 90K was observed in this device. The second QDIP device is similar to the first one except that In 0.45Ga0.55P is used as the current blocking layer. The third QDIP device is a 10-period 2.7-ML InAs QD/500 A GaAs spacer without current blocking layer. The results show that the thicker GaAs spacer is more effective than the large bandgap In0.45Ga0.55P current blocking layer to improve QDIP performance. The fourth QDIP device is a 10-period 5 ML In0.6Ga0.4As QDs with 600A GaAs spacer. The peak detection wavelength shifts from 7.6mum to 8.4mum when the temperature rises from 40K to 260K. The peak background limited performance detectivity at 77K and -2.0V is 1.1 x 1010cm-Hz1/2W. This QDIP has achieved the highest operation temperature (260K) and performance characteristics among the QWIPs and QDIPs reported in the literature.; Finally, a two-stack QDIP structure was designed to achieve multi-color detection in long-wavelength infrared region. The top stack is composed by 8-period 2.6ML In0.5Ga0.5As QDs with a 500 A GaAs spacer, and the bottom stack consists of 8-period 2.6ML InAs QDs with a 500 A GaAs spacer. Photoresponse peak at around 7.9∼9mum was observed in the top stack up to 130K, and two peaks (7.2mum, 10.6mum) were found in the bottom stack up to 110K.; The key contributions of this work include the demonstration of a high-operation temperature QDIP and the development of a novel 3-color QWIP and several QDIPs that have potential use in the 3∼5 mum and 8∼14 mum infrared focal plane array (FPA) application.