Measurement of the In0.52Al0.48As valence-band hydrostatic deformation potential and the hydrostatic-pressure dependence of the In0.52Al0.48As/InP valence-band offset

We have measured the In0.52Al0.48As valence-band hydrostatic deformation potential from the hydrostatic-pressure dependence of the In0.52Al0.48As/InP valence-band offset which was measured from 0 to 35 kbar at room temperature. Due to the type-II band lineup, the radiative recombinations across the InP band gap and between the InP conduction band and the In0.52Al0.48As valence band were both observed in the photoluminescence spectra. This enables us to measure directly the changes of the valence-band offset under pressure. The hydrostatic-pressure derivative of the valence-band offset was measured to be 0.00.4 meV/kbar. The predictions of the pressure dependence from band-offset models (dielectric midgap and model-solid theories) agree with the measurement to within 1 meV/kbar. The In0.52Al0.48As valence-band hydrostatic deformation potential is found to be -0.8 eV which compares well with the dielectric midgap theory. Using the reported pressure dependence of the GaAs/AlAs valence-band offset, the valence-band hydrostatic deformation potentials of InxAl1-xAs (0x0.52) are linearly interpolated as -1.9x+0.2 eV

RESONANT TUNNELING DEVICES

The physics of resonant tunneling is as yet a research topic and has been discussed at some length elsewhere in this conference. The subject of this paper, devices using the phenomenon of resonant tunneling, is one which is in its infancy. Nevertheless, it is of great interest to examine the present state and to explore some of the directions which research is taking in the study of resonant tunneling devices. Among other things, these devices offer the possibilities of very high speed and very small size, and thus advantages for very large scale integration

VERY LARGE PHOTOVOLTAIC EFFECTS IN MODULATION-DOPED HETEROSTRUCTURES

Nous avons mis en evidence l'existence d'un effet photovoltaique dans les heterojonctions a dopage module de faible densite bidimensionelle. Des photovoltages lateraux de l'ordre de la centaine de millivolts apparaissent entre deux contacts ohmiques distants d'environ 1 cm lorsqu'un faisceau laser de quelques microwatts est focalise sur la surface de l'echantillon. L'effet est attribue a la separation des porteurs dans la region de l'heterojonction. L'intensite du photovoltage depend fortement de la position du spot laser par rapport aux contacts, et sature pour les larges puissances d'excitation, ce qui rend cet effet directement utilisable pour un dispositif optoelectronique.We report the observation of large in-plane photovoltages in low electron density modulation doped heterostructures. Local optical excitations of the order of microwatts are found to produce lateral photovoltages as high as several hundred millivolts between contacts centimeters away from the exciting spot. The effect is attributed to the vertical photovoltage locally induced by the separation of the photocreated electrons and holes. Its strong position dependence as well as its saturability are shown to be attractive for technological applications

Excitons in semiconducting superlattices, quantum wells, and ternary alloys

Semiconducting layered structures can now be fabricated with precisely defined layer thicknesses down to one monolayer. An example is the superlattice'' (SL) structure, in which to semiconductors with different band gaps are interleaved. The electronic and optical properties of the SL are quite different from those of the constitutents and offer interesting new possibilities both in device design and in basic physics. This proposal aims to improve our understanding of optically excited states in SL's, particularly in the so-called Type 2 indirect'' SL's in which in electron and hole created by optical excitation are separated both in real and in momentum space. We study these structures by time-resolved tunable laser spectroscopy, with and without external perturbations such as magnetic field, electric field, and uniaxial stress. In SLs with only a few atomic layers per period the familiar effective mass model'' of semiconductor states breaks down. We have made precise optical experiments on well-characterized material to test current first principles'' calculations of the band structure. Our work under this grant has shown that the material we are using is of sufficiently high quality to test the theoretical predictions. Comparison of theory and experiment provides a new and sensitive probe of the interface quality on a fine scale. Statistical analysis of the temperature dependence of the exciton decay dynamics provides complementary information. From a careful study of the exciton spectra of the recently discovered mixed type 1- type 2 CdTe/CdZnTe SLs we have obtained the band offset at the CdTe/CdZnTe interface to unprecedented accuracy

Real-time Optical Diagnostics For Measuring And Controlling Epitaxial Growth

We summarize recent applications of two real-time optical diagnostic techniques, reflectance difference spectroscopy (RDS) and spectroellipsometry (SE), to epitaxial growth on GaAs and atomic layer epitaxy (ALE) in particular. Using RDS, we obtain the first real-time spectroscopic data of the evolution of the (001) GaAs surface to cyclic and non-cycle exposures of atmospheric pressure H2, H2 and trimethylgallium, and H2 and arsine, which simulate growth by ALE. None of our observations is consistent with any previously proposed simple model, emphasizing the necessity of real-time measurements for the analysis of complex surface reactions. Using SE we have constructed a closed-loop system for controlling the compositions of AlxGa1-xAs layers grown by chemical beam epitaxy. We have produced various graded-compositional structures, including parabolic quantum wells 200 Å wide where the composition was controlled by analysis of the running outermost 3 Å (about 1 monolayer) of depositing material. © 1993.22501/02/152631Goodman, Pessa, (1986) J. Appl. Phys., 60, p. R65. , and references cited thereinOzeki, Ohtsuka, Sakuma, Kodama, (1991) J. Cryst. Growth, 107, p. 102Ozeki, Mochizuki, Ohtsuka, Kodama, (1988) Appl. Phys. Lett., 53, p. 1509Nishizawa, Kurabayashi, Abe, Sakurai, Gallium arsenide thin films by low-temperature photochemical processes (1987) Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 5, p. 1572Yu, Buchan, Souda, Kuech, Surface Chemistry and Mechanism of Atomic Layer Growth of GaAs (1991) MRS Proceedings, 222, p. 3Creighton, Banse, The Surface Chemistry of GaAs Atomic Layer Epitaxy (1991) MRS Proceedings, 222, p. 15Aspnes, Harbison, Studna, Florez, (1987) Phys. Rev. Lett., 59, p. 1687Aspnes, Harbison, Studna, Florez, Application of reflectance difference spectroscopy to molecular-beam epitaxy growth of GaAs and AlAs (1988) Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 6, p. 1327Kobayashi, Horikoshi, (1989) Jpn. J. Appl. Phys., 28, p. L1880Kobayashi, Horikoshi, Pyrolysis of Trimethylgallium on (001) GaAs Surface Investigated by Surface Photo-Absorption (1991) Japanese Journal of Applied Physics, 30, p. L319Aspnes, Quinn, Gregory, (1990) Appl. Phys. Lett., 57, p. 2707Aspnes, Quinn, Tamargo, Pudensi, Schwarz, Brasil, Nahory, Gregory, (1992) Appl. Phys. Lett., 60, p. 1244Aspnes, Kamiya, Tanaka, Bhat, Atomic layer epitaxy on (001) GaAs: Real-time spectroscopy (1992) Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 10, p. 1725Kamiya, Aspnes, Tanaka, Florez, Harbison, Bhat, (1992) Phys. Rev. Lett., 68, p. 627Kamiya, Aspnes, Florez, Harbison, (1992) Phys. Rev. B, 46, p. 15894Gomyo, Suzuki, Iijima, (1988) Phys. Rev. Lett., 60, p. 2645Froyen, Zunger, (1991) Phys. Rev. Lett., 59, p. 324Chen, Stringfellow, (1991) Appl. Phys. Lett., 59, p. 324Chiu, (1989) Appl. Phys. Lett., 55, p. 1244Creighton, (1990) Surf. Sci., 234, p. 287Memmert, Yu, (1990) Appl. Phys. Lett., 56, p. 1883Aspnes, Colas, Studna, Bhat, Koza, Keramidas, (1988) Phys. Rev. Lett., 61, p. 2782Reflectance–difference studies of organometallic chemical vapor deposition growth transients on (001) GaAs (1989) Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 7, p. 711Farrell, Harbison, Peterson, Molecular-beam epitaxy growth mechanisms on GaAs(100) surfaces (1987) Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 5, p. 1482Annapragada, Salim, Jensen, Ftir Studies Of Organometallic Surface Chemistry Relevant To Atomic Layer Epitaxy. (1991) MRS Proceedings, 222, p. 81Studna, Aspnes, Florez, Wilkens, Ryan, Low-retardance fused-quartz window for real-time optical applications in ultrahigh vacuum (1989) Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 7, p. 3291Aspnes, Studna, (1975) Appl. Opt., 14, p. 220(1978) Rev. Sci. Instrum., 49, p. 291Aspnes, Bhat, Colas, Florez, Gregory, Harbison, Kamiya, Wassermeier, Real-Time Optical Diagnostics For Measuring And Controlling Epitaxial Growth (1991) MRS Proceedings, 222, p. 63. , 2nd ed