摘要:

Techniques used to fabricate a gated resonant tunneling diode (GRTD) are presented. Molecular‐beam epitaxy (MBE), image reversal contact photolithography, liftoff metallization, anisotropic reactive ion etching, isotropic liquid etching, and a resulting self‐aligned gate metal deposition technique were used to realize this effort. The physical sizes of the fabricated GRTDs were 2, 4, and 6 μm in diameter. The electrical size of the channel within the vertical resonant tunneling diode, however, was controlled by a simple, self‐aligned rectifying electrode at the well region. Arrays of devices were fabricated to enhance detection while retaining small geometries. The results from these first devices indicate that aninsitutransition from a two‐dimensional resonant tunneling diode (RTD) to a zero‐dimensional quantum dot is feasible using this design. Improvements in the design are realizable from straightforward modifications in the MBE material.

ISSN:0734-211X    

DOI:10.1116/1.585032

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Silicon nitride films were deposited by the plasma‐enhanced chemical vapor deposition (PECVD) method in a silane and nitrogen atmosphere as encapsulants for rapid thermal annealing of Si‐implanted GaAs. The deposition rate and refractive index of PECVD silicon nitride films were measured with varying the radio‐frequency (rf) power, chamber pressure, N2/SiH4ratio, and substrate temperature. A wide range of deposition parameters was used, and this range of rf power dependence has not been previously reported.

ISSN:0734-211X    

DOI:10.1116/1.585034

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Effects of ion‐beam and chemical etching on the optical properties of GaAs were studied by means of cathodoluminescence. An important degradation of the radiative properties is observed at the surface as well as in depth. This degradation is not removed by the ohmic contact annealing process at 450 °C. In the case of chemical etching, a complex behavior of the luminescence properties after annealing is indicative of surface‐states modifications. To optimize the etching procedure, we defined a process combining an ion‐beam etching at 250 eV and a short‐duration chemical etching.

ISSN:0734-211X    

DOI:10.1116/1.585035

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

As a result of the photowashing of (100)n‐GaAs (n≊3×1016cm−3) a decrease of about 25% in the surface potential was found using the contactless electromodulation method of photoreflectance. This corresponds to a reduction in the surface state density by about a factor of 2.

ISSN:0734-211X    

DOI:10.1116/1.585036

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Results are presented on the first state‐resolved optical detection of As2in a molecular‐beam epitaxy (MBE) reactor. Using the technique of laser induced fluorescence (LIF) on theA 1∑+u–X 1∑+gtransition, the gas phase populations of vibrational and rotational states of As2emanating from a commercial As4oven‐cracker source are probed. A Boltzmann fit of the populations of the first four vibrations indicates that these states are thermalized to the source temperature (source: 1050±25 K; vibrations: 1020±100 K). Likewise, the rotational manifold of each vibration is consistent with thermalization at the same temperature. The sensitivity of the LIF technique is sufficient to characterize a flux of 3×1014As2cm−2 s−1. Therefore, the method is capable of being aninsitureal‐time MBE diagnostic. Optical detection may provide complementary information to reflection high‐energy electron diffraction (RHEED) that would not otherwise be available. Future applications of this technique may lead to new insights into epitaxial growth processes.

ISSN:0734-211X    

DOI:10.1116/1.585037

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Important corrections are required for x‐ray diffraction characterization of epitaxial AlxGa1−xAs grown on offcut GaAs substrates. These corrections can have technological impacts for thin film fabrication where precise and reproducible process control is required. Double crystal x‐ray diffraction measurements of AlxGa1−xAs grown on an offcut GaAs(100) substrate are interpreted in terms of a three step distortion of the film unit cell producing ‘‘defect free’’ heteroepitaxy: the film unit cell is first tetragonally, then triclinicly distorted, and finally tilted with respect to the substrate unit cell. The results indicate that the unit cell distortion and tilt angles oppose each other, forming a crystal geometry where the vector normals of the film and substrate (100) planes are approximately coplanar with the vector normal of the substrate’s surface. The film unit cell is triclinicly distorted in a way such that the film 〈100〉 axis remains approximately parallel to the substrate 〈100〉 axis. Application of conventional x‐ray diffraction formalism based on a tetragonal distortion of the film unit cell to this more complicated unit cell geometry, can result in significant errors. Double crystal x‐ray diffraction formalism is presented which accounts for a triclinic distortion and external tilt of the AlxGa1−xAs unit cell, leading to correct measurement of the film concentration and film/substrate crystal geometry.

ISSN:0734-211X    

DOI:10.1116/1.585038

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

We have used reflection high‐energy electron diffraction to investigate the influence of substrate temperature, arsenic pressure, and Al composition on the growth of tilted superlattices(TSLs) on atomically stepped surfaces. In the temperature range of 450–675 °C, we found that GaAs and TSLs grow smoother at high temperatures and low arsenic pressures. In the same range, AlAs grows smoother at low temperatures and high arsenic pressures. We also found that raising the AlAs composition of TSLs raises the substrate temperature required for pure step flow growth. We have also found new evidence that a low‐temperature, smooth‐surface growth regime for AlGaAs exists below 450 °C.

ISSN:0734-211X    

DOI:10.1116/1.585039

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Submicrometer periodic patterns were fabricated by spatial period division (SPD) using synchrotron radiation. The spectrum bandwidth was controlled to nearly the optimum width by using a W/Be multilayer mirror. This reduces the influence of gap variations between the x‐ray mask and the Si wafer.

ISSN:0734-211X    

DOI:10.1116/1.585040

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Synchrotron radiation x‐ray lithography, using commercial x‐ray masks, has been used in a mix‐and‐match scheme with an optical stepper to fabricate functional 0.3 μm gate‐lengthn‐type metal–oxide–semiconductor devices. The x‐ray exposures were done at the Center for X‐ray Lithography (CXrL) at the University of Wisconsin‐Madison. The gate‐level mask was fabricated to our specifications by Perkin‐Elmer Advanced Lithography Operations, Danbury, CT. All other processing and the optical stepper exposures were carried out at the McDonnell Douglas Electronics Systems Company—Microelectronics Center, St. Louis, MO. Processing results and device characteristics are discussed.

ISSN:0734-211X    

DOI:10.1116/1.585041

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

The influence of absorber and membrane stresses on x‐ray mask distortions were examined both by simulation and experiments. The boundary element method was used for the numerical simulation of the distortions. Investigations were focused on the distortions appearing in the bulk‐Si etching step of the subtractive x‐ray mask fabrication method. Distortion measurements were performed using two types of masks in order to investigate the distortions caused by only the membrane stress and both the absorber and membrane stresses, separately. The simulated results show good agreement with the experimental results. Some guidelines to suppress the process‐induced distortions were derived by the simulation. The value of the product of stress and thickness of the membrane must be restricted to within 10×104dyn/cm in order not to deform the Si frame. Pattern position shift is almost suppressed when the membrane stress is nearly equal to the absorber stress. The membrane stress should be controlled to values slightly larger than the absorber stress. If the mask is constructed of a 1 mm thick, 3 in. diam Si frame having a 23×23 mm window region with a Ta stress of 1×108dyn/cm2, the SiN membrane stress should be controlled in the region of 1–4×108dyn/cm2. This condition limits the shift in position of patterns arranged within the window region to less than 0.03 μm (3σ).

ISSN:0734-211X    

DOI:10.1116/1.585042

出版商:American Vacuum Society    

年代:1990

数据来源: AIP