Inas Quantum Dot Infrared Photodetectors With Ingaas Covering Layers Of Materials, Molecular Beam Epitaxy

The concepts of semiconductor super-lattice and quantum well pioneered a new area of designing and fabricating low-dimensional artificial materials with quantum structures.The quantum dot(QD) that is restricted in three dimensions has unique quantum effects,which has attracted more and more attention and been an international research hot spot.InAs and InGaAs quantum dots grown on GaAs substrates have enormous potential advantages in laser and infrared detector applications.In this paper,self-assembled InAs QDs are grown by molecular beam epitaxy(MBE) on(001) GaAs substrates capped with InGaAs layer with graded Indium composition,and then quantum dot infrared photo-detectors(QDIP) are fabricated.After systematical characterizations and investigations on the InAs QD structures and QDIP devices,the following conclusions are drawn:1.The surface morphology and luminescent characteristics of QDs::By adopting an appropriate growth temperature and arsenic pressure,a slower deposition rate and growth interruptions,the QD sizes and distribution density has been optimized.Atomic force microscopy(AFM) measurements show that the QD sizes and distribution are uniform,density and high aspect ratio increased.Full width at half maximum of photoluminescence(PL) spectra is narrowed and the intensity is increased.2.The Characteristic of devices:By inserting an InGaAs layer with graded Indium composition on top of the QD active layer,the graded InGaAs layer released the stress of the QDs,suppressed the Indium segregation in the QDs,enhanced the quality of the epitaxial layer,lowered the barrier height,and caused a red shift of the PL peak wavelength of the InAs QDs.Volt-ampere characteristic and photocurrent(PC) spectra measurements show that the infrared respondence of the devices has been improved with the optimized growth conditions, the responding wavelength has an obvious red-shift for the device capped with an InGaAs layer with graded Indium composition.These results have fulfilled our research purpose,and have great significance on improving the photo-electronic performance of QDIPs...