摘要:

Comparison studies of N‐doping of ZnSe for (100) and (311)A orientations have been performed. TheC–Vmeasurements indicated that the doping level of the samples grown on (311)A is higher than that of the samples on (100). Doping experiments using Zn3As2as As‐doping source evaporated by a Knudsen effusion cell also have been performed. Low‐temperature photoluminescence measurements revealed evidence of shallow acceptor bound excitons, indicating that some of the As is being incorporated as shallow levels. It is also pointed out that group V monomers such as As and P are promisingp‐type dopants.

ISSN:0734-211X    

DOI:10.1116/1.587042

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Carbon doping in III–V compounds has generated much attention because of applications in high temperature and high current devices. We present results using a novel electron beam carbon source for doping GaAs and GaSb. The source construction allows normal effusion cell geometry and utilizes electron bombardment for evaporation from a carbon rod. Mass spectrometer data showed the carbon flux contained C1, C2, and C3species. For GaAs, controllable hole doping densities between 3×1015cm−3and 5×1019cm−3were obtained. For GaSb, carbon doping resulted inP‐type material with hole densities ranging from the background level of 2×1016to 3×1020cm−3for specular film morphology. Hole mobility values for GaAs and GaSb are comparable to published data.

ISSN:0734-211X    

DOI:10.1116/1.587043

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The mobility behavior of boron delta (δ)‐doped Si, Si1−xGex(0≤x≤1) is investigated, which includes the first mobility measurements reported for B δ‐doped Si1−xGexand Ge. The expected mobility enhancement from δ doping is not realized in Si:B due to the heavy effective mass of holes. However, some enhancement may be possible at lower doping levels for narrower wells. Indications of mobility enhancement have been realized for δ‐doped Ge:B because of the relatively light effective mass. We also present the implementation of boron δ‐doped layers in the fabrication of (i) the first SiGe:B δ‐FET and (ii) the first coupled δ‐layer Si:B δ‐FET.

ISSN:0734-211X    

DOI:10.1116/1.587044

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Pyrometric interferometry (PI) has recently been demonstrated for simultaneous real time wafer temperature and thickness measurement during the molecular beam epitaxy process. Both parameters of the thin film layer can be determined from the changing interference conditions in the layer. We used a reflection assisted version of PI to follow the thermal history of the wafer under different conditions and were able to resolve temperature to less than 1 °C. For thickness measurements, a parabolic fitting algorithm was used to accurately determine the endpoints of the GaAs/AlAs quarter wave stacks. Compared to other noncontact methods this technique can be used for very thick layers and is unaffected by the layer absorption and optical effects.  

ISSN:0734-211X    

DOI:10.1116/1.587045

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The use of ellipsometry as an alternative technique forinsitudetermination of molecular beam epitaxial growth parameters has been demonstrated. Epitaxial growth has been monitored in real time using three discrete wavelengths to extract growth rates and alloy composition. The effect of substrate rotation on the measured growth rates has also been determined by this technique. From measurements of the GaAs growth rates versus substrate temperature, a value of 4.68±0.12 eV for the activation energy for Ga desorption during GaAs growth was obtained. This agrees with values obtained by other measurement techniques.

ISSN:0734-211X    

DOI:10.1116/1.587046

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Temperature‐dependent optical constants (30 °C

ISSN:0734-211X    

DOI:10.1116/1.587047

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

We have developed a stable (<1% drift/h at 1 Å/s), fast (∼200 ms), sensitive (S/N∼10–200 at 1 Å/s) evaporation rate monitor for controlling electron beam sources. Based on dual beam atomic absorption spectroscopy (AAS), in which a reference arm compensates for drift in the light source and signal detection apparatus, this technique is very wavelength and hence element specific, allowing many elements to be simultaneously and independently monitored. Furthermore, the system can operate at very high background gas pressures, as well as under ultrahigh vacuum conditions. Also, because only the light must enter the vacuum chamber and pass through the evaporant, minimal periodic maintenance inside the chamber is necessary. The versatility and sensitivity of this AA system make it a viable candidate forinsitumonitoring of various other thin film processes, including sputtering, ion milling, and reactive ion etching.

ISSN:0734-211X    

DOI:10.1116/1.587048

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A theoretical model was developed to simulate the apparent substrate temperature oscillation during the growth of AlAs/AlxGa1−xAs,x=0 and 0.25, distributed Bragg reflectors (DBR) for 980‐ and 780‐nm vertical cavity surface emitting lasers, respectively. The simulated data were then used forinsitumonitoring and feedback control of layer thickness by a simple pyrometric interferometry technique to obtain a highly reproducible DBR. These measurements can be performed with continuous substrate rotation and without any growth interruption. The reproducibility of the center wavelength and full width at half‐maximum of the reflectivity stop band with a variation of<±0.2% and<±0.4% for the AlAs/GaAs and AlAs/AlGaAs mirror stacks, respectively, were achieved.

ISSN:0734-211X    

DOI:10.1116/1.587049

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The temperature of GaAs substrates is profiled in a molecular‐beam epitaxy system with a spatial resolution of 3 mm and a thermal resolution of 0.4 °C, respectively. The effects of substrate doping, back surface textures, thermal contact to the holder, and a pyrolytic boron nitride diffuser plate, on the temperature uniformity, are explored for indium‐free mounted substrates. Both positive and negative curvature temperature profiles are observed.

ISSN:0734-211X    

DOI:10.1116/1.587050

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The molecular beam epitaxy (MBE) process is generally surrounded by liquid nitrogen (LN2) cooled surfaces for optimum control of the environment in which the thin‐film deposition takes place. The design and operation of a LN2supply system for feeding the cryogenicly cooled surfaces in a MBE system is described here. The supply system is based on modification of a standard 50‐lLN2storage dewar. The reservoir gravity feeds liquid through a vacuum‐insulated line into the fill port of the MBE system. A solenoid‐operated vent valve activated by a temperature controller regulates the level of LN2in the MBE system. The LN2supply system is efficient and costs much less than other alternatives.

ISSN:0734-211X    

DOI:10.1116/1.587051

出版商:American Vacuum Society    

年代:1994

数据来源: AIP