摘要:

Anisotropic etching of GaAs(100) is performed using a hot Cl2molecular beam produced by free expansion of gas heated in a furnace. The etch rate is 1.5 μm/min at a furnace temperature of 800 °C and a substrate temperature of 120 °C. An aspect ratio of ten and an almost smooth bottom surface are obtained under this condition.

ISSN:1071-1023    

DOI:10.1116/1.585647

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We studied the doping characteristics of Si into molecular‐beam epitaxially grown InAlAs layers for various growth conditions. The growth temperature and V/III beam flux ratio proved to play different roles in Si doping. The growth temperature affects the Si doping concentration, and the V/III flux ratio does the compensation ratio. AtTs=560 °C, a rather high temperature for the growth of InAlAs layers, the Si doping concentration reached 150% as compared with growth atTs=500 °C. With increasing V/III flux ratio, on the other hand, electron mobility and donor concentration increased, suggesting a decreased compensation ratio. We also found a considerable number of electron trapping centers at a low‐growth temperature of 400 °C.

ISSN:1071-1023    

DOI:10.1116/1.585648

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Precise control of the compositional profile in ternary semiconductors, with the resulting spatial variation of band structure, allows electronic and/or optical properties to be tailored for specific applications. An algorithm is presented, and its implementation described, for the growth of very narrow graded compositional GaAs/AlGaAs heterostructure wells and barriers by conventional solid‐source molecular beam epitaxy. The Al source furnace temperature is controlled continuously to obtain linear analog compositional grading. Physical confirmation of the precision of the profiles has been obtained by a range of techniques including secondary ion mass spectrometry, secondary neutral mass spectroscopy, and compositional analysis from thickness fringes‐transmission electron microscopy. The results show excellent linearity and symmetry in structures with compositional changes between 0% and 30% Al over 10‐nm graded regions.

ISSN:1071-1023    

DOI:10.1116/1.585649

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

The development of optical lithography has promoted the development of ultralarge scale integration (ULSI) devices. However, optical lithography is now facing serious obstacles due to the limitations in wavelength. Higher resolution with sufficient depth of focus is the most important requirement for ULSI engineers. To satisfy this requirement, many technologies for resolution improvement and new optical image formation technologies such as phase shifting and focus latitude enhancement exposure (FLEX) are reviewed, and a future perspective on optical lithography is also discussed in this paper.

ISSN:1071-1023    

DOI:10.1116/1.585650

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Coupled GaAs/GaAlAs rings have been fabricated using electron‐beam lithography and wet chemical etching. We report the first observation of conductance steps associated withe2/hin etched structures, and clear Aharonov–Bohm oscillations in multiple rings connected in parallel. The amplitude of the oscillations is found to be dependent on the number of rings indicating the possibility of phase coupling between electrons traversing different rings.

ISSN:1071-1023    

DOI:10.1116/1.585651

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Nanometer scale patterns have been fabricated in SiO2by direct electron‐beam exposure. Two techniques have been developed to eliminate the surface contamination and enable the subsequent development of the patterns in HF based wet etches: (1) exposing the oxide through a sacrificial layer (previously reported) and (2) O2reactive ion etching (RIE). The latter approach eliminates the need for a sacrificial layer and improves resolution by reducing the forward scattering of the beam. To determine the resolution of this process, patterns were fabricated with both 50‐ and 300‐kV electrons in thin SiO2membrane samples and imaged in transmission. Transmission imaging avoids the resolution limit of secondary electron micrographs set by the lateral range of secondary electrons. At 300 keV with a line dose of 7.5 μC/cm, arrays of lines with a period down to 15 nm were achieved as opposed to the 21‐nm period previously reported using a sacrificial layer and secondary electron imaging of bulk substrates. A better understanding has also been obtained of the profiles of the patterns in SiO2.

ISSN:1071-1023    

DOI:10.1116/1.585652

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We report the fabrication and characterization of facetless Bragg reflector surface‐emitting AlGaAs/GaAs lasers. Both first‐order (120‐nm period) and second‐order (240‐nm period) gratings were fabricated by electron‐beam lithography and chemically assisted ion‐beam etching (CAIBE). These grating pairs provide the optical feedback of the laser, eliminating the need for cleaved or etched mirror facets. Specifically, this work includes: the fabrication and testing of a variable pitch grating‐laser array which demonstrates optical emission peaks with 5‐Å separation for adjacent lasers; demonstration of facetless Bragg reflector lasers with 120/240‐nm grating pairs that show lower threshold currents, higher quantum efficiencies, and improved beam width compared to conventional facetless second‐order grating lasers; and a demonstration of grating surface‐emitting diode lasers with hybrid first‐order and nonresonant, 120/307‐nm, grating pairs that produced a directed beam at 45° with respect to the substrate. The fabrication technology and optical performance of these devices are presented.

ISSN:1071-1023    

DOI:10.1116/1.585653

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A fabrication process has been developed for making free‐standing gratings of silicon nitride. These structures are critical components of an atom interferometer, which uses four gratings as coherent beam splitters of atom waves. The quality of gratings necessary for an interferometer is considerably higher than is needed to demonstrate the diffraction of atoms. In particular, the gratings must be phase coherent over their entire area. This implies that the grating lines must be straight to the order of their linewidth over the full extent of the grating. In addition, the open fraction of the grating structure is more critical for an interferometer. In this paper the development of new fabrication techniques that were used to make free‐standing gratings with periods as small as 100 nm and support structure open fractions as high as 0.8 were reported on. To achieve depth‐to‐linewidth ratios greater than 4:1 with grating periods as small as 100 nm a selective, highly directional reactive ion etching (RIE) process has been developed.

ISSN:1071-1023    

DOI:10.1116/1.585654

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

In this paper we report on an exploratory metal oxide semiconductor field effect transistor (MOSFET) device which we are currently investigating which requires 100 nm lithography at all critical levels to achieve a completely fully scaled 100 nm device structure. The device also incorporates a novel trench isolation scheme whereby the isolation trenches are etched after the gate electrodes have been formed leading to a butted gate configuration. The device further incorporates fully overlapped contacts to the gate, source, and drain regions in order to provide maximum contact area. We believe that this structure will provide a good basis for exploring the density and performance limits of 100 nm‐scale devices. We describe here the structure of the proposed device and then we propose a suitable method of fabrication. This is followed by a demonstration of suitable nanofabrication techniques which are based, in each case, on high resolution electron beam lithography and precision reactive ion etching. Finally, we assess the feasibility of integrating these techniques in order to realize the proposed device.

ISSN:1071-1023    

DOI:10.1116/1.585655

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We report on techniques for fabricating 20‐nm scale ballistic electron devices and on techniques for imaging and characterizing these patterns in thin layers of poly(methylmethacrylate) (PMMA). A split‐gate fabrication approach with nanometer‐scale Schottky gates is used. Using a multiple layer PMMA resist technique, we have fabricated Au/Pd gates as narrow as 20 nm. In order to enhance the undercut profile a lower molecular weight PMMA is used as the bottom layer. We have also developed a resist stabilization technique which allows the viewing of 20 nm scale features in 0.1‐μm thick PMMA resist under high magnification in a scanning electron microscope. These techniques have been used to fabricate ballistic electron devices which demonstrate quantum interference effects.

ISSN:1071-1023    

DOI:10.1116/1.585656

出版商:American Vacuum Society    

年代:1991

数据来源: AIP