Showing papers by "Werner Wesch published in 1989"

Defect production during ion implantation of various AIIIBV semiconductors

Abstract: The present paper gives a survey about the defect generation caused by ion implantation of GaAs, InAs, GaP, and InP. By combining Rutherford backscattering spectrometry, optical spectroscopy, and transmission electron microscopic methods, further information concerning the kinetics of the defect production as well as the type of defects created is obtained. Generally, the defect concentration in the region of implantation parameters investigated can be described by the energy density deposited into nuclear processes. Below critical values of the nuclear deposited energy density in GaAs weakly damaged layers containing point defects and point defect clusters are produced. With increasing nuclear deposited energy density an increasing number of amorphous zones is created due to manifold overlap of the initial defect clusters. The results indicate that in GaAs and InAs already at relatively low implantation temperatures, the amorphization occurs via homogeneous defect nucleation. The results obtained for GaP...

Defects in Weakly Damaged Ion‐Implanted GaAs and Other III–V Semiconductors

Abstract: Under definite implantation conditions (small ion masses, sufficiently small ion fluences, and high implantation temperature) in III–V compounds weakly damaged layers are produced, which exhibit characteristic properties near the optical edge and an only slight increase of dechanneling of backscattered light ions. Especially for GaAs, InP, and GaP an exponential dependence of the near edge absorption coefficient on the photon energy according to K ∼ exp (ħω/E1) with E1 = 0.52 eV for GaAs, 0.33 eV for InP, and 0.6 eV for GaP is observed. From theoretical considerations it is concluded that this behaviour is connected with the existence of high concentrations of complexes containing antisite defects and vacancies. Combining optical measurements with TEM and measurements of the temperature dependence of the dechanneling gives further information about the structure of weakly damaged GaAs layers. The results of a complex analysis of weakly damaged GaAs and other III–V compound layers and first ideas about the damage structure in such layers are discussed. In III–V-Verbindungshalbleitern entstehen unter bestimmten Implantationsbedingungen (niedrige Ionenmassen, hinreichend niedrige Ionendosis und hohe Implantationstemperatur) schwach geschadigte Schichten, die charakteristische optische Eigenschaften im Bereich der Bandkante aufweisen und zu einer nur geringen Erhohung der Dekanalisierung ruckgestreuter leichter Ionen fuhren. Insbesondere findet man in GaAs, InP und GaP im Bereich der Bandkante eine exponentielle Anhangigkeit des Absorptionskoeffizienten von der Photonenenergie entsprechend K ∼ ∼ exp (ħω/E1) mit E1 = 0,52 eV fur GaAs, 0,33 eV fur InP und 0,6 eV fur GaP. Aus theoretischen Untersuchungen kann gefolgert werden, das dieses Verhalten mit der Existenz einer hohen Konzentration von Defektkomplexen verbunden ist, die Antisite-Defekte und Vakanzen enthalten. Erganzende Untersuchungen mittels TEM und zur Temperaturabhangigkeit der Dekanalisierung liefern weitere Informationen uber die Struktur der schwach geschadigten GaAs-Schichten. Es werden die Ergebnisse einer komplexen Analyse schwach geschadigter GaAs- und anderer III—V-Halbleiterschichten und erste Vorstellungen uber die Struktur der Defekte in diesen Schichten diskutiert.

Investigation of defects in weakly damaged ion implanted GaAs layers

Abstract: From the analysis of the near edge optical properties it has previously been concluded that weakly damaged ion implanted GaAs layers contain high concentrations of point defect complexes consisting preferably of vacancies and anti-site defects. The investigation of the temperature dependence of the dechanneling of light ions provides further information about the structure of such layers. With this method it was shown that, in room temperature nitrogen implanted GaAs, slightly and heavily displaced atoms exist with mean values of the displacement distance r a = 0.018 nm and r a = 0.065 nm from the atomic strings, respectively. The concentrations of the two defect types varies with the ion fluence. The results indicate that defect annealing and recombination during room temperature implantation of GaAs produces a resulting damage structure consisting of point defect complexes which contain vacancies and anti-site defects. As the implant fluence is increased the formation of further defects (interstitials also) becomes probable.

Investigation of Low‐Temperature Epitaxial Regrowth of Ion‐Implanted Amorphous GaAs

Abstract: A detailed description of optical reflectivity technique for monitoring laser-induced solid phase epitaxial regrowth in real time is given. An example illustrates the use of this technique for the investigation of interface structures. By cooling the sample the epitaxial regrowth of the crystalline/amorphous interface is stopped before the interface reaches the surface. These stages are additionally investigated by TEM- and RBS-studies which illustrate the dependence of the crystalline quality on the regrowth process. Es wird eine genaue Beschreibung der optischen Echtzeitreflexionstechnik zur Aufzeichnung von laserinduzierter Festphasenepitaxie gegeben. Die Anwendung dieser Methode zur Untersuchung der Struktur der Phasengrenze wird an einem Beispiel gezeigt. Bevor die kristallin/amorphe Phasengrenze die Oberflache erreicht, wird die Epitaxie durch Kuhlung gestoppt. Diese Zustande werden zusatzlich durch TEM- und RBS-Messungen untersucht. Sie zeigen die Kristallqualitat in Abhangigkeit vom Wachstumsprozes.