Title :
Electrical and optical bandgaps of Gex Si1-x strained layers
Author :
Jain, S.C. ; Poortmans, Jozef ; Iyer, Srikanth S. ; Loferski, J.J. ; Nijs, J. ; Mertens, Robert ; Overstraeten, R.
Author_Institution :
Div. of Eng., Brown Univ., Providence, RI, USA
fDate :
12/1/1993 12:00:00 AM
Abstract :
Theoretical and experimental evidence is presented to show that the effective mass of holes is reduced due to strain in the Gex Si1-x layers grown on Si(100) substrate. It is shown theoretically that due to this change in the hole effective mass, the reduction of bandgap of a heavily doped (i.e., more than ~1×1018 cm-3) GexSi1-x strained layer base determined by measuring the collector current of the heterostructure bipolar transistor (HBT) is smaller than the bandgap reduction obtained from optical measurements. When uncertainties in the value of the mass and in the experimental results are taken into account, agreement between the theoretical and experimental bandgap reduction values is satisfactory. A significant result obtained is that a high Ge and doping concentrations in the base suppress the collector current and make it smaller than the value that would be obtained if heavy doping effects are neglected
Keywords :
Ge-Si alloys; effective mass (band structure); energy gap; heavily doped semiconductors; heterojunction bipolar transistors; optical constants; semiconductor epitaxial layers; semiconductor materials; Gex Si1-x strained layers; GeSi-Si; Si; Si(100) substrate; bandgap reduction; collector current; electrical bandgap; heavily doped strained layer base; heavy doping effects; heterostructure bipolar transistor; hole effective mass; optical bandgap; Capacitive sensors; Current measurement; Density measurement; Doping; Electric variables measurement; Energy measurement; Heterojunction bipolar transistors; Laboratories; Photonic band gap; Temperature dependence;
Journal_Title :
Electron Devices, IEEE Transactions on
