Optical properties of silicon(1-x) germanium(x)/silicon quantum wells and superlattices for device applications.

摘要

Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si heterostructures have received considerable interest in recent years because of their novel optical and high speed device applications. The major advantage of the Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si material system is its compatibility with the current Si-VLSI technology. Fabrication of novel optical devices (infrared detectors, lasers and optical modulators) will make a great impact on optoelectronics, since these devices can be monolithically integrated with Si-VLSI circuits. Motivated by this, optical properties of Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si quantum wells and superlattices have been investigated in this dissertation. The samples used in the experiments have been grown by the Si/Ge molecular beam epitaxy (MBE) technique.; This dissertation consists of four main subjects which reveal the optical properties of Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si quantum wells, superlattices and Si {dollar}delta{dollar}-doped quantum wells, and discuss the realization of novel optical devices using Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si structures. In chapters 4 through 6 the experimental results of the intersubband transitions will be discussed. The incoming photon polarization field dependent absorption spectra are in good agreement with the intersubband transition selection rule. The heavy doping effects on the intersubband absorption, especially peak transition energy, are quantitatively investigated by employing the self-consistent calculation which incorporates many-body effects. Intersubband transitions between minibands in Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si superlattices are also observed. In this case, carriers are externally injected to minibands at the resonant condition.; Using p-type Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si multiple quantum wells, long wavelength ({dollar}{lcub}sim{rcub}10 mu{dollar}m) infrared detectors are fabricated. These detectors exhibit normal incidence detection. The measured peak responsivity is about 0.3 A/W at 77 K, and estimated detectivity ({dollar}Dsp*{dollar}) is about 1.0 {dollar}times{dollar} 10{dollar}sp9{dollar} cm {dollar}sqrt{lcub}rm Hz{rcub}{dollar}/W for 7 {dollar}sim{dollar} 10 {dollar}mu{dollar}m at 77 K. The performance of the detector and the physics involved in the normal incidence detection will be discussed in chapter 7.; In chapter 8, the first observation of normal incidence intervalence-subband infrared transition in p-type Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si multiple quantum wells will be discussed. The transition energy and the peak absorption strength are shown to be a strong function of the Ge concentration in the well. The physics of this transition will be discussed. Also, based on this infrared transition, other normal incidence infrared detectors have been fabricated. The measured photoresponse will also be presented.; Finally, in chapter 9, the first observation of large interband Stark shift in type-II Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si multiple quantum wells will be discussed. The results show large red shift of the absorption edge which is about 0.7 {dollar}sim{dollar} 1 meV kV{dollar}sp{lcub}-1{rcub}{dollar} cm. This suggests the application of type-II Si{dollar}sb{lcub}rm 1-x{rcub}{dollar}Ge{dollar}sb{lcub}rm x{rcub}{dollar}/Si structures for the electro-optics devices near 1.3 {dollar}mu{dollar}m.