Strained Si/SiGe heterostructures for device applications

Abstract A review is given of the most recent developments in the field of strained Si/SiGe heterostructures for transistor applications. Main topics are the pseudomorphic SiGe-base heterobipolar transistor (HBT) and modulation-doped field effect transistors (MODFET) utilizing strain-adjusting SiGe buffer layers. Si/SiGe HBTs have recently demonstrated transit frequencies in excess of 100 GHz, thus improving the high frequency cut-off of the best Si bipolar junction transistors (BJT) by a factor of two. They are now on their route from mere lab-demonstrators into the production lines. Si/SiGe MODFETs are at an earlier state, having just solved one of the most stringent material problems, namely the epitaxial growth of a relaxed SiGe buffer layer with low defect densities. This allowed the realization of n -type and p -type quantum well structures with unprecedentedly high carrier mobilities. p -type MODFETs with pure Ge channels have been fabricated on Si substrates recently. These are very promising devices for complementary applications in combination with Si-channel n -type MODFETs because of the almost perfectly matched carrier mobilities. Beside basic material aspects and physical properties, d.c.-results of test devices demonstrating superior transconductances will be treated.

[1]  H. Jorke,et al.  Mobility Enhancement in Modulation‐Doped Si ‐ Si1 − x Ge x Superlattice Grown by Molecular Beam Epitaxy , 1986 .

[2]  U. Konig,et al.  Enhancement mode n-channel Si/SiGe MODFET with high intrinsic transconductance , 1992 .

[3]  John C. Bean,et al.  Modulation doping in GexSi1−x/Si strained layer heterostructures , 1984 .

[4]  D.D. Tang,et al.  A scaled 0.25- mu m bipolar technology using full e-beam lithography , 1992, IEEE Electron Device Letters.

[5]  F. Schäffler,et al.  Two-dimensional electron gas properties of symmetrically strained Si/Si1−xGex quantum well structures , 1990 .

[6]  J. N. Albers,et al.  DC characteristics and stability behaviour of high-speed Si/SiGe HBTs with undoped SiGe spacer between base and collector , 1992 .

[7]  J. Nocera,et al.  High-transconductance n-type Si/SiGe modulation-doped field-effect transistors , 1992, IEEE Electron Device Letters.

[8]  E. Kasper.  Growth and properties of Si/SiGe superlattices , 1986 .

[9]  Gerhard Abstreiter,et al.  High-electron-mobility Si/SiGe heterostructures: influence of the relaxed SiGe buffer layer , 1992 .

[10]  J. Sturm,et al.  Graded-base Si/Si/sub 1-x/Ge/sub x//Si heterojunction bipolar transistors grown by rapid thermal chemical vapor deposition with near-ideal electrical characteristics , 1991, IEEE Electron Device Letters.

[11]  J.M.C. Stork,et al.  Graded-SiGe-base, poly-emitter heterojunction bipolar transistors , 1989, IEEE Electron Device Letters.

[12]  Martin,et al.  Theoretical calculations of heterojunction discontinuities in the Si/Ge system. , 1986, Physical review. B, Condensed matter.

[13]  G. Abstreiter,et al.  High electron mobility in modulation‐doped Si/SiGe quantum well structures , 1991 .

[14]  D. Harame,et al.  75-GHz f/sub T/ SiGe-base heterojunction bipolar transistors , 1990, IEEE Electron Device Letters.

[15]  E. Fitzgerald,et al.  Comparison of mobility‐limiting mechanisms in high‐mobility Si1−xGex heterostructures , 1993 .

[16]  T. Kamins,et al.  Small-geometry, high-performance, Si-Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors , 1989, IEEE Electron Device Letters.

[17]  Abstreiter,et al.  Magnetotransport measurements and low-temperature scattering times of electron gases in high-quality Si/Si1-xGex heterostructures. , 1992, Physical review. B, Condensed matter.

[18]  Jurgen Michel,et al.  Totally relaxed GexSi1−x layers with low threading dislocation densities grown on Si substrates , 1991 .

[19]  Herbert Kroemer,et al.  Theory of a Wide-Gap Emitter for Transistors , 1957, Proceedings of the IRE.

[20]  U. Erben,et al.  MBE-grown Si/SiGe HBTs with high beta , f/sub T/, and f/sub max/ , 1992, IEEE Electron Device Letters.

[21]  LeGoues,et al.  Anomalous strain relaxation in SiGe thin films and superlattices. , 1991, Physical review letters.

[22]  Bernard S. Meyerson,et al.  High electron mobility in modulation‐doped Si/SiGe , 1991 .

[23]  Don Monroe,et al.  Relaxed GexSi1−x structures for III–V integration with Si and high mobility two‐dimensional electron gases in Si , 1992 .

[24]  F. Schaffler,et al.  Operating CMOS after a Si-MBE process: a precondition for future three-dimensional circuits , 1990, IEEE Electron Device Letters.

[25]  Don Monroe,et al.  Extremely high electron mobility in Si/GexSi1−x structures grown by molecular beam epitaxy , 1991 .

[26]  F. Schaffler,et al.  p-type Ge-channel MODFETs with high transconductance grown on Si substrates , 1993, IEEE Electron Device Letters.

[27]  Wolf,et al.  Strain-induced two-dimensional electron gas in selectively doped Si/SixGe1-x superlattices. , 1985, Physical review letters.

[28]  R. J. Hawkins,et al.  Limitations of Nielsen's and related noise equations applied to microwave bipolar transistors, and a new expression for the frequency and current dependent noise figure , 1977 .

[29]  Z. A. Shafi,et al.  Predicted propagation delay of Si/SiGe heterojunction bipolar ECL circuits , 1990 .

[30]  J. Sturm,et al.  The effects of base dopant outdiffusion and undoped Si/sub 1-x/Ge/sub x/ junction spacer layers in Si/Si/sub 1-x/Ge/sub x//Si heterojunction bipolar transistors , 1991, IEEE Electron Device Letters.