Study Of Hole Intersubband Transition In Si/SiGe Quantum Well And Its Application In Mid-/Far- Infrared Light Emitter And Detector

People have won tremendous successes in silicon microelectronic technique,but, bulk silicon,with a indirect bandgap has a five order of magnitude lower light emission efficiency than direct bandgap materials such as GaAs.So,how to realize high light emission efficiency of silicon-based materials is one of the important topics concerning the development of silicon-based optoelectronics.Energy band engineering by using the intersubband transition in Si/SiGe quantum wells has been recognized as one of promising approaches to achievement of efficient light emission from silicon-based materials.In last few years,high-performance silicon-based mid-/far- infrared optoelectronic devices attracted more attention in academe and industry.It is therefore tremendously important to carry out such works for developing science,technology and industry for national defense in our country.Against this major background,a basic study has been carried out on Si/SiGe quantum cascade lasers and Si/SiGe quantum well infrared detectors based on hole intersubband transitions.The main work and results are summarized as follows:1.The valence band structures and hole effective masses of strained Si/SiGe materials are systematically studied by using the 6×6 k·p method.Holes occupation in the highly Boron doped quantum wells,the momentum matrix elements and optical absorption of intersubband transition between two hole states have been numerically calculated.2.The energy band design and operational mechanism of Si/SiGe quantum cascade lasers(QCLs) at mid-/far- infrared(terahertz) frequency are discussed.By using Drude model and FDTD method,high confinement factor of Si/SiGe QCLs work at THz frequency are obtained with low loss coefficients.3.Designs for strained p-type Si/SiGe quantum well infrared photodetectors(QWIPs) based on the bound-to-quasi-bound transitions are discussed,the figure-of-merit of this kind of Si/SiGe QWIPs have beed calcuated.We proposed on tensile strained p-type QWIPs for the first time,which are expected to retain the ability to couple normally incident infrared radiation without any grating couplers,with lower dark current than that of n-type QWIPs and larger absorption coefficient and better transport characteristics than those of normal unstrained or compressive strained p-type QWIPs.4.High quality Si/SiGe QWIP structures were expitaxially grown by using UHV/CVD system.A method was developed to evaluate the growth rates and Ge compositions of Si/SiGe quantum wells.The equilibration time for the source gases to deposit on Si substrate can also be evaluate by this method.5.Infrared absorption spectra of the Si/SiGe QWIP structures have been measured and the QWIP devices were fabricated.The FTIR measuremmts show that the Si/SiGe QWIP structure has a strong absorption at 3～5μm,this wavelength range is one of the Earth's atmosphere in the transparent spectral regions.