摘要:

The activation kinetics of acceptors was investigated for heteroepitaxial layers of GaN, doped with Mg. After growth, the samples were exposed to isochronal rapid thermal anneals in the temperature range from 500 to 775 °C. The samples were studied by variable temperature Hall effect measurements and photoluminescence (PL) spectroscopy in the as‐grown condition and after each temperature step. The thermal treatment reduced the resistivity by six orders of magnitude and thep‐type conductivity was found to be dominated by an acceptor with an activation energy of ∼170 meV. This acceptor is attributed to Mg atoms substituting for Ga in the GaN lattice and the activation process is consistent with dissociation of electrically inactive Mg–H complexes. It is shown that the appearance of a blue emission band in the PL spectrum of Mg‐doped GaN does not directly correlate with the increase inp‐type conductivity. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116503

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

This work reports on the effect of postdeposition thermal treatment using rapid thermal annealing on the physical and electrical properties of metalorganic chemical‐vapor‐deposited (MOCVD) titanium nitride (TiN) thin films. When ammonia is used as the annealing ambient, the resistivity decreases with increasing annealing temperature. The resistivity of MOCVD TiN was reduced from 6000 to 320 &mgr;&OHgr; cm after 800 °C rapid thermal annealing in ammonia (RTN). Annealing in nitrogen ambient was found to be not nearly as effective as that in ammonia. The decrease in resistivity may be attributed to a reduction in the carbon and oxygen content, growth in grain size through polycrystalline recrystallization, as well as to an increase in film density. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116586

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The onset of misfit dislocation generation in [001] In0.2Ga0.8As/GaAs single heterostructures is investigated by transmission electron microscopy using the liftoff technique. To determine the equilibrium critical thickness of misfit dislocation generation for different temperatures, postgrowth annealing was carried out for 2 h at 530 and 600 °C. The equilibrium critical thicknesses are determined as 100–120 A˚ for 530 °C postgrowth annealing and 60–80 A˚ for 600 °C postgrowth annealing, respectively. Metastable dislocation structures can be disturbed by sustained elevated temperatures. The variability in the effect is once again due to variations in the extent of dislocation pinning. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116587

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The strong bias dependence of the far‐infrared laser‐induced negative photoeffect is here attributed to an intrinsic bias dependent internal photoemission effect. Experimental results fit remarkably well with the carrier temperature and the transition potential predicted by our model. We demonstrate that any asymmetric heavily doped junction (P+/N,N+/P) which is properly forward biased is suitable to detect far infrared radiation. The sensitivity is reasonable (≊1 mV per kW at 300 K) for detection of pulsed radiation and the rise time is intrinsically fast (≤1 ns). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116588

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Schottky diodes with patterned overlayers of thin metal films have provided a method to measure the energy loss of high energy electrons in the metal films. The technique avoids the problems of surface contamination and electron collection which complicate measurements on freestanding films. The patterned overlayer creates a modulation in the reverse biased diode current as a beam of focused electrons is moved across the diode surface. The amplitude of the modulation has been measured with overlayers of aluminum and gold for incident electron energies of 5 to 30 keV. The results have been compared to that predicted from a Monte Carlo calculation of the inelastic and elastic scattering of the incident electrons. Significantly better agreement between experiment and simulation is observed when the screened Rutherford cross section in the Monte Carlo code is replaced by an empirical expression for the Mott scattering formula. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116589

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

2&thgr; and pole figure x‐ray analysis have been used to examine the crystal structure and orientation of Ag films deposited on GaAs(100) substrates cleaned by a variety of wet etches. Where epitaxy was observed, it was of the type Ag(110)/GaAs(100). The H3PO4/HCl sequential etch yielded the film with the highest degree of preferred orientation, with the H2SO4/HCl, NH4OH, and HF etches producing films of decreasing quality in the order named. The epitaxial quality is thought to scale with elemental As concentration on the GaAs(100) surface, and have an inverse relationship to the amount of surface oxides present before deposition. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116590

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the fabrication and characterization of ap‐type porous silicon/n‐type hydrogenated amorphous silicon (a‐Si:H)pn‐heterojunction electroluminescent device structure. The devices exhibit electroluminescence in forward bias, demonstrating minority carrier injection fromn‐typea‐Si:H intop‐type porous silicon. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116591

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The electrical conduction of free‐standing porous silicon layers, obtained fromn+silicon with various anodization currents and illumination conditions, has been investigated in vacuum as a function of the temperature in the interval 300‐210 K. The two‐contactI‐Vcharacteristic is determined by the metal/porous silicon rectifying interface, whereas, by using the four‐contact technique, a linear dependence of the current vs voltage was found. The resistance of free‐standing samples showed a thermally activated behavior, with activation energies ranging from 0.1 to 0.44 eV. It was found that the activation energy decreased if the light intensity during the anodization was reduced. Variations of activation energy were also observed if the anodization current was changed but, in this case, it was not possible to find any correlation over the parameter range investigated. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116592

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

SrBi2Ta2O9(SBT) thin films are known to exhibit no polarization fatigue with electric field cycling. However, we have discovered that optical illumination combined with a bias voltage near the switching threshold can result in significant (≳90%) suppression of the switchable polarization of SBT thin film capacitors. A similar effect has also been reported for Pb(ZrxTi1−x)O3(PZT) capacitors. However, it is found that electric field cycling of the optically fatigued SBT capacitors results in near‐complete recovery of the suppressed polarization. In contrast, electric field cycling of optically fatigued PZT capacitors does not result in any polarization recovery. These results suggest that optical fatigue in both SBT and PZT capacitors results from pinning of domain walls due to trapping of the photogenerated carriers at domain boundaries, whereas the recovery exhibited by SBT thin films indicates that the domain walls are more weakly pinned in SBT than in PZT thin films. Consequently, the fatigue‐free behavior of SBT thin films during electric field cycling can be viewed as a competition between domain wall pinning due to charge trapping and domain wall unpinning by the cycling field; the latter process occurring at least as rapidly as the former. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116593

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Surface imperfections of silicon‐on‐insulator (SOI) wafers are investigated by means of extremely asymmetric x‐ray reflection topography, in which the glancing angle of the incident x rays is near the critical angle of total reflection; this geometry is achieved by using tunable wavelength synchrotron radiation. Two kinds of SOI wafers: bonded and two oxygen implanted silicon wafers are used as samples. The experimental topographs reveal a characteristic contrast for each sample, which cannot be observed by conventional x‐ray topography. The observed contrasts strongly depend on the fabrication techniques of the SOI wafers. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116594

出版商:AIP    

年代:1996

数据来源: AIP