Ako Hatano

A study on strong memory effects for Mg doping in GaN metalorganic chemical vapor deposition

Mg doping response was studied for GaN metalorganic chemical vapor deposition (MOCVD) for the first time. The delay time was observed between Mg atom incorporation into the growing layer and supplying Mg source to the reactor, in spite of the quick response for doping turn off. The delay time increased steeply with decreasing Mg source flow rate. The delay was considered to originate from adsorption of Mg source molecules to the reactor wall (memory effect). A large Mg sticking coefficient and the existence of a saturated amount of Mg source molecules adsorbed to the reactor wall were suggested. Reducing the memory effect by purging the inlet nozzle of the reactor with the mixed source gas to be used to grow next layer during growth interruption, the doping responce was improved significantly and Mg concentration was controlled down to 5 × 10 16 cum −3

Growth of High-Quality AlN and AlN/GaN/AlN Heterostructure on Sapphire Substrate

Metalorganic chemical vapor deposition (MOCVD) growth of AlN on sapphire substrates was investigated, with the aim of device quality AlN/GaN/AlN double heterostructures. Growth temperature as high as 1300° C was required to obtain AlN epitaxial layers with sharp X-ray diffraction peaks. By growing AlN at the high growth temperature, residual stress at the heterointerface was effectively reduced. The AlN epitaxial layers with smooth surfaces were grown using a low V/III ratio together with the high growth temperature. AlN/GaN/AlN double heterostructures with appropriate layer thicknesses for DH lasers and flat heterointerfaces were grown on sapphire substrates.

H-atom incorporation in Mg-doped GaN grown by metalorganic chemical vapor deposition

H-atom incorporation was studied for Mg-doped GaN grown by metalorganic chemical vapor deposition. H-atom incorporation was found to increase linearly with Mg concentration, suggesting the formation of simple complex between Mg and H atoms in GaN. Decrease of H-atom concentration was observed after thermal treatment in Ar, supporting the hypothesis that H-atom extraction plays an important role in obtaining low-resistivity p-type conduction.

New magnesium doping source for metalorganic chemical vapor deposition: Octamethyldialuminummonomagnesium

Octamethyldialuminummonomagnesium (an adduct of trimethylaluminum and dimethylmagnesium) is proposed as an alternative candidate for an Mg doping source in metalorganic chemical vapor deposition. Water cooling for the reactor wall was important to prevent predecomposition of the adduct. Almost flat doping profiles were obtained independent of Mg concentration. Long doping tails were not observed. The doping efficiency was independent of substrate temperature between 600 and 700 °C, indicating a lower decomposition temperature for this Mg source. It was suggested that carrier concentration control can be improved by removing Si containing impurities from this Mg source.

Magnesium doping using an adduct of trimethylaluminum and dimethylmagnesium in metalorganic chemical vapor deposition

Abstract Mg doping for metalorganic chemical vapor deposition of Ga 1− x Al x As, using octamethyldialuminummonomagnesium (an adduct of trimethylaluminum and dimethylmagnesium), was studied as a function of Al composition and growth conditions. The Mg incorporation efficiency increased with decreasing growth temperature, and the maximum concentration was as high as 2.3 × 10 20 cm -3 at a growth temperature of 700°C for GaAs. An increase in Mg incorporation efficiency was seen with increasing Al composition, suggesting less Mg re-evaporation from the growing surface for layers with higher Al compositions. The limiting maximum attainable concentration values seemed to reach the same value, independent of Al composition. Long doping transients, as reported in the literature, were not observed. The doping response was essentially unchanged independent of Al composition.