Search

Pseudomorphic In x Ga1-x As/Al0.28Ga0.72As (x = 0.085–0.15) quantum wells (QWs) with well widths of 1.2, 2.4, 3.6, 4.8, 7.2 and 12 nm have been grown on (411)A and (100) GaAs substrates at a temperature (T s) of 520°C by molecular beam epitaxy (MBE). The interface flatness of the QWs was characterized by photoluminescence (PL) at 4.2 K. PL linewidths of the narrow (411)A QWs (L w = 2.4 nm) with x = 0.085 and 0.15 were 7.3 meV which is approximately 30–40% smaller than those of the (100) QWs, indicating that extremely flat interfaces over a macroscopic area [(411)A super-flat interfaces] have been realized in the pseudomorphic In x Ga1-x As/Al0.28Ga0.72As QWs (up to x = 0.15) grown on the (411)A GaAs substrates, similar to lattice-matched GaAs/Al x Ga1-x As QWs grown on (411)A GaAs substrate previously reported.

Effectively atomically flat interfaces over a macroscopic area (super-flat interfaces) have been achieved in pseudomorphic In x Ga1-x As/Al0.3Ga0.7As (x = 0.0, 0.04, 0.07) quantum wells (QWs) with well widths (L w) of 1.2–11.8 nm grown on (411)A GaAs substrates at 520°C by molecular beam epitaxy (MBE). A single, sharp photoluminescence (PL) peak was observed for each QW over the large area of the wafer (8 mm ×5 mm). The linewidths for narrow QWs (L w = 2.4 nm) were 8.9 meV (x = 0.04) and 9.9 meV (x = 0.07) at 4.2 K, which were about 30% smaller than those of QWs simultaneously grown on conventional (100) GaAs substrates.

GaAs/Al0.3Ga0.7As tilted T‐shaped quantum wires (T‐QWRs) were fabricated by growing Al0.3Ga0.7As/GaAs (well thickness of GaAs Lw=4.4 nm) on a (111)B facet plane that was formed when a GaAs/Al0.3Ga0.7As multi‐quantum well (MQW) layer (Lw=4.5 nm) was grown on a reverse‐mesa etched GaAs(100) substrate by glancing‐angle molecular beam epitaxy (GA‐MBE). Growth conditions of the tilted T‐QWR were optimized, and full width at half‐maximum (FWHM) of a cathodoluminescence (CL) peak from the tilted T‐QWRs was reduced down to 19 meV at 78 K, which is about one‐third of that (61 meV) of previous GaAs/Al0.3Ga0.7As tilted T‐QWRs.

A new type of CO 2 sensor based on electrical conductivity changes was developed using porous hydroxyapatite ceramics. Starting powders prepared by the usual wet process were cast in film with an organic vehicle and fired on alumina substrates after electrodes had been arranged. It was necessary to soak the samples in a CaCl 2 solution in order to make them reactive with Co 2 . Both d.c. and a.c. measurements were carried out in various atmospheres including air, CO 2 and air containing different amounts of CO 2 . D.c. measurements suggested that the carrier would be one of the space charges such as protons and other ions. It was confirmed by a.c. measurements that the sample possessed fundamental sensor characteristics.