摘要:

Structurally integrated silicon nitride layers have been formed on the surface of crystalline silicon, using the process of nitrogen ion implantation. The as‐implanted as well as thermally regrown samples have been examined using a thin layer sensitive internal friction technique and infrared transmission measurements. The types of defects formed due to the implantation process and their activation energies have been obtained, along with the information regarding the recovery of the defective as‐implanted state during thermal annealing. The internal friction apparatus used in the mechanical measurements on thin silicon reeds is based on the design of Berryetal., wherein one essentially looks for the damping of a resonant flexural mode of oscillation of the reed sample as a function of temperature in a vacuum of 10−6Torr. This allows one to obtain the information regarding the defect induced anelasticity in thin crystalline samples at an atomic level. In the present case, we have identified defects having activation energies of 0.5 and 0.65 eV produced due to implantation and their transformation into another defect state of activation energy 0.8 eV during thermal treatment. It has been established that the ion‐bombardment process leaves the silicon layers with a large percentage of self‐interstitials in a strain field. The thermal annealing leads to a release of the structural strain and a development of the silicon–nitride phase. The possibility and importance of using the internal friction technique in studying the interface defects in metastable and modulated semiconductor structures are discussed.

ISSN:1071-1023    

DOI:10.1116/1.582565

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We have extended our calculations for defect levels at semiconductor free surfaces to ideal semiconductor heterojunctions. We find that the Fermi‐energy pinning observed for deposition of Ge and Si (as well as metals and oxygen) on GaAs(110) surfaces is explained very satisfactorily by free‐surface antisite defect levels, but cannot be explained, even qualitatively, by antisite defect levels for bulk GaAs or for ideal GaAs/Ge or GaAs/Si interfaces. We conclude that when pinning occurs at heterojunctions and at other semiconductor/overlayer interfaces, the pinning defects are somehow ‘‘sheltered’’ by irregularities in the atomic configurations at the interface.

ISSN:1071-1023    

DOI:10.1116/1.582566

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We present optical and magnetotransport experiments performed in InGaAs–InP heterojunctions and superlattices grown by metalorganic chemical vapor deposition. These investigations give evidence of the two‐dimensional nature of these new structures, and also some information on their electronic properties.

ISSN:1071-1023    

DOI:10.1116/1.582613

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We present near band gap optical transmission experiments in a series of GaSb–AlSb superlattices grown by molecular beam epitaxy. The spectra exhibit a steplike behavior characteristic of two‐dimensional electron systems. The absorption steps are attributed to transitions between valence and conduction states confined in the GaSb quantum wells. However, the energy of the absorption edge is smaller than that expected for a simple well, probably as a result of the effect of strain.

ISSN:1071-1023    

DOI:10.1116/1.582614

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The plasma oscillations of layered electron systems in modulation doped GaAs–(AlGa)As heterostructures were investigated by inelastic light scattering. These experiments are the first to probe the dispersion of the plasma frequency in multiple semiconductor heterostructures. The measured dispersions are linear in the in‐plane component of wave vector. These results confirm predictions of the layered electron gas model.

ISSN:1071-1023    

DOI:10.1116/1.582615

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We present a simple theory of the dielectric function in superlattices. The calculation is performed separately for different symmetry points of the band structure. We assume that among the contributing states only the Γ states are influenced substantially by size quantization and the electronic states at Γ are calculated by using a simplifiedk⋅pmethod. New features of the dielectric constant of superlattices are a fine structure due to zone folding (subbands) and a small anisotropy due to the lower symmetry. Except for these finer details, the index of refraction of a superlattice is well approximated by the corresponding constant for an alloy Alx̄Ga1−x̄As wherex̄ is the averaged Al mole fraction of the superlattice.

ISSN:1071-1023    

DOI:10.1116/1.582616

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The photoluminescence (PL) spectra of undoped GaAs substrates which are partly covered by a modulation‐doped AlxGa1−xAs/GaAs structure show a remarkable new effect at low temperature (T<100 K). When a voltage is applied between two Ohmic contacts to the modulation‐doped structure such that a current flows parallel to the interface, the near band edge PL spectra shift slowly toward lower energies with an accompanying reduction in intensity. After removing the bias, the spectra gradually recover to their original position and intensity. The time constants for this behavior vary from sample to sample and range from between a few minutes to more than an hour. The asymptotically approached magnitude of the spectral shift is a monotonic function of the applied voltage. Its value is approximately 18 meV for an 8 V applied bias. The direction and magnitude of shift are independent of the sign of the bias and are uniform over the total area of the sample. The modulation‐doped structure can be reduced in lateral dimensions to a small area containing the two Ohmic contacts, and the spectra of the substrate measured several millimeters away from the modulation‐doped area still show the described effect. Optical absorption measurements through the substrate show a corresponding shift of the band gap absorption edge toward lower energies thus confirming that the effect occurs throughout the bulk.

ISSN:1071-1023    

DOI:10.1116/1.582617

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We report the first observation of the oscillatory magnetic moment as a function of the magnetic field (deHaas–van Alphen effect) of a two‐dimensional electron gas. The measurements were performed at 1.5 K on a modulation‐doped GaAs–(AlGa)As heterostructure using a SQUID magnetometer. The strength of the signal was enhanced by stacking 4000 layers equivalent to an area of 240 cm2. The data are in qualitative agreement with theory but the amplitude of the oscillations is about a factor of 30 weaker than expected. We attribute this discrepancy to sample inhomogeneities. More accurate measurements should allow a direct determination of the electronic density of states.

ISSN:1071-1023    

DOI:10.1116/1.582618

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The collective excitations of doped (or modulated doped) semiconductor superlattices are investigated. We focus primarily on the GaAs–Ga1−xAlxAs (type‐1) superlattice in the limit that the quantum wells are far enough apart that wave function overlap between wells is negligible. The plasmon‐type excitations under study here are driven entirely by long range Coulomb interaction between wells. In particular, we will discuss superlattice plasmons, LO‐phonon superlattice plasmons, magnetosuperlattice plasmons, acoustic and optic plasmons for diawell superlattices, intersubband depolarization superlattice plasmons, and hybrid superlattice–intersubband depolarization plasmons. A novel realization of a structure which has tunable plasmons is suggested.

ISSN:1071-1023    

DOI:10.1116/1.582620

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The energy spectra of a multivalley quantum well structure are investigated by both the tight‐binding and the effective‐mass methods. It is shown that the energy spectrum as a function of the quantum well width exhibits an interference pattern due to the mixing of Bloch states of the well material with wave vectors near the two equivalent conduction band minima.

ISSN:1071-1023    

DOI:10.1116/1.582621

出版商:American Vacuum Society    

年代:1983

数据来源: AIP