A method is described which makes full use of the data gathered in measuring the elastic constants and internal friction of small samples undergoing free decay. A Fourier transform approach is employed which first determines accurately the period and starting phase of the free decay and checks the purity of the signal. This information is then used along with the original data to determine the internal friction of the sample.

GaAs surface cleaning prior to molecular-beam epitaxy (MBE) using a new hydrogen radical beam produced by an electron cyclotron resonance plasma in an ultrahigh-vacuum system is investigated. Residual oxygen and carbon on the GaAs surface after cleaning are monitored in situ with Auger electron spectroscopy. Oxygen and carbon, which are hard to remove by conventional thermal cleaning, can be removed by hydrogen radical (H*) beam irradiation at a substrate temperature of <400 °C. It is verified that the plasma-dissociated radicals are much more reactive in the gas phase–solid phase surface chemical interaction than the nondischarged molecules. Ga and As stoichiometry is kept after H* beam cleaning. Good crystallinity is obtained according to reflection high-energy elecron diffraction. By carrier concentration measurement at the interface between the cleaned surface and the in situ MBE-regrown layer, it is found that H* beam cleaning reduces the interface state concentration. This cleaning technique makes clean GaAs surfaces available for MBE pretreatment.

GaAs and GaAlAs equi-rate etchings, which are difficult in the conventional reactive ion etching (RIE), have been achieved by using Cl2 plasma flux in a new reactive ion beam etching (RIBE) system. The system has an ultra-high-vacuum (UHV) design basis and several plasma monitors for investigating an elementary etching process. The establishment of the equi-rate etching has been presumed as due to the possible elimination of particles contributing to the aluminum-oxide or other non-volatile material formation, such as C, O2 and H2O.

Articles you may be interested inChemical dry etching of GaAs and InP by Cl2 using a new ultrahigh-vacuum dry-etching molecular-beam-epitaxy system Damage and contamination-free GaAs and AlGaAs etching using a novel ultrahigh-vacuum reactive ion beam etching system with etched surface monitoring and cleaning method GaAs and AIGaAs have been crystallographic ally etched with low-pressure chlorine radicals in an electron-cyclotron resonance (ECR) plasma shower with a new reactive-ion-beam etching (RIBE) system for obtaining damage-and contamination-free etching. The etching begins abruptly at 190°C and increases gradually above 2(Xrc. The typical etching rate ofa (001) plane is I/!m/min at a substrate temperature of 300°C. Mesa-shaped and reverse mesa-shaped grooves with {IIIL side wall planes are obtained for (110)-and (HO)-oriented line and space masks.For square masks with [ 110 1 edge lines, on the other hand, high aspect-ratio columns with {I OO} vertical side wall planes are obtained. These results show that the etching rate of { Ill} A is much lower than that of{ lOO}, {11O}, or {l1l}B' AIGaAs is etched similarly to GaAs. Cl 2 gas (not plasma excited) performs similar etching. However, the substrate temperature must be about 100 °C higher for the beginning of etching than for the Cl radical etching. These etching technologies are promising for microfabrication of GaAsl AlGaAs optoelectronic devices, replacing conventional wet chemical etching.

I n situ monitoring and suppression of damage and contamination induced by GaAs and AlGaAs reactive-ion-beam-etching (RIBE) have been investigated to establish clean surfaces, required for fabricating III–V compound optoelectronic integrated circuits (OEIC’s). A novel ultrahigh-vacuum RIBE system with etched surface monitors and a surface cleaning gun has been developed for this purpose. Damage suppression with low energy (10–100 eV) RIBE was confirmed with an ideality factor in a Schottky diode. Removal of Cl contamination induced by Cl2 plasma was established with temperature-controlled (200 °C) RIBE or heat treatment (400 °C) after RIBE. Furthermore, it was demonstrated for the first time that both GaAs and AlGaAs native oxide layers could be successfully removed simply with irradiations of H and Cl radical beam released from the novel, compact electron-cyclotron-resonance (ECR) plasma gun.