Selective area control of material properties in laser-assisted MOVPE of GaAs and AlGaAs

Transient annealing of ion implanted GaAs

Because of the specific properties of GaAs, the annealing of implantation damage as well as the electric activation of dopants present more complez processes compared with silicon. Starting from the problems connected with conventional furnace annealing of GaAs, the results obtained with short time annealing in the solid and liquid phase are discussed. By means of liquid phase epitaxy using ns-laser pulses, extremely high carrier concentrations can be achieved, but the mobility of the carriers is limited by matrix-specific defects. Optical and RBS investigations give information about the defect types existing in pulsed laser irradiated GaAs layers, and the connection with the electrical properties of the layers is demonstrated. Possible ways for a reduction of the concentration of such defects as well as the improvement of the electrical properties are discussed.



Auf Grund der spezifischen Eigenschaften von GaAs ist die Ausheilung von Strahlenschaden in diesem Material ein weitaus komplexerer Prozes als im Silizium. Ausgehend von den Problemen bei der konventionellen Ofenausheilung von GaAs werden die mit Hilfe von Kurzzeitausheilverfahren im Festphasen- und Flussigphasenregime erzielten Ergebnisse diskutiert. Bei der mit ns- Laserimpulsen realisierten Flussigphasenepitaxie konnen extrem hohe Ladungstragerkonzentrationen erzeugt werden. Die Beweglichkeit der Ladungstrager wird jedoeh durch matrixspezifische Defekte begrenzt. Mit Hilfe von optischen und RBS-Messungen werden Aussagen uber die nach Flussigphasenepitaxie vorhandenen Defekttypen gemacht, der Zusammenhang mit den elektrischen Eigenschaften wird demonstriert. Mogliche Wege zur Verringerung der Konzentration derartiger Defekte sowie zur Erzielung verbesserter elektrischer Eigenschaften werden diskutiert.

Rapid annealing of ion-implanted GaAs†

Deep level transient spectroscopy (d.l.t.s.) has been applied to the study of deep levels in GaAs following post-implantation annealing using a Q-switched ruby laser. High concentrations (> 1015 cm?3) of deep trapping levels are observed in the laser melt region using a forward-bias voltage pulse.

Laser annealing of low dose Se-implanted GaAs studied by d.l.t.s.

Damage removal of Se+‐implanted InP after cw Ar+ laser annealing has been monitored by measurement of the optical extinction coefficient k. A gradual decrease in k as a function of laser power is observed for room‐temperature ion‐implanted InP samples, compared to a sharp decrease in k for ion‐implanted Si. These data and electrical measurements indicate that the ion‐implantation damage removal process for InP is more complex than for Si.

cw laser‐annealing behavior of Se+‐implanted InP investigated by ellipsometry

GaAs samples implanted at room temperature with selenium ions at energies in the range 100–800 keV were annealed with a Q-switched ruby laser. The annealing was carried out in air, with no protective layer on the GaAs samples. The percentage electrical activity was found to depend on the implanted dose, ion energy, laser energy density and the substrate temperature during laser annealing. The mobilities of the electrically activated atoms were generally lower than the expected values. However, these were found to increase when the samples were thermally annealed subsequent to the laser irradiation. Low dose implants, i.e. less than 1.1014 cm-2, previously shown to be insensitive to laser annealing, have been successfully annealed in this work when the substrates were held at 200°C during laser annealing.

Improvement in Electrical Properties of Laser Annealed Ion Implanted GaAs

Laser annealing of GaAs implanted at room temperature with 1.1015 or 5.1015 ions/cm2 of Te+, Se+, Sn+ and Ge+ ions has been studied. Depending on the dose, a single pulse from a Q‐switched ruby laser produced, in general, electron concentrations in excess of 1.1019 cm−3 for both coated and non‐coated samples. However, mobility values were low, indicative of the presence of a large concentration of ionised impurities. Significant indiffusion of Te nd Sn atoms was observed following laser irradiation.

B. J. Sealy

Papers

Improvement in Electrical Properties of Laser Annealed Ion Implanted GaAs

Laser annealing of ion implanted GaAs