High-efficiency InGaAlP surface emission light emitting diodes (LEDs) have been successfully fabricated. Newly designed double-heterostructure LEDs with a GaAlAs current spreading layer were employed to expand the light emission area, which is necessary to take out the light efficiently. The external quantum efficiency was 1.5% at 620 nm orange light for an In0.5 (Ga0.8Al0.2)0.5P active layer LED. This LED is five times more efficient at 620 nm than that of the GaAlAs and GaAsP LEDs. 563 nm green electroluminescence, which is the shortest wavelength ever reported for InGaAlP LEDs, was also achieved with an In0.5(Ga0.5Al0.5)0.5P active layer.
Room-temperature cw operation for InGaP/InGaAlP double heterostructure (DH) laser diodes on GaAs substrates was achieved for the first time. The DH wafers were grown by low-pressure metalorganic chemical vapor deposition using methyl metalorganics. A lasing wavelength of 679 nm and a threshold current of 109 mA at 24 °C were obtained for an inner stripe structure laser diode with a 250-μm-long and 7-μm stripe geometry. The laser operated at up to 51 °C. The characteristic temperature T0 was 87 K at around room temperature. The lowest threshold current density, 5.0 kA/cm2, was obtained with a 20-μm stripe width laser diode under room-temperature pulsed operation.
Candela class InGaAlP surface-emission green light-emitting diodes (LEDs) have been successfully fabricated. The growth of InGaAlP on an intentionally misoriented substrate improved emission properties, as confirmed by a quantitative estimation of the diffusion length in the active material. A Bragg reflector using InGaAlP was realized for the first time. A new device structure, including this Bragg reflector, drastically improved the light extraction efficiency. An external quantum efficiency of 0.7% at 573 nm green light was obtained, corresponding to a luminous intensity of 2 cd.
Bi 4Àx La x Ti 3 O 12 (BLT) ferroelectric thin films were prepared on a Pt/TiO x /SiO 2 /Si substrate using metalorganic decomposition (MOD) method, and their electrical properties were evaluated with thickness, composition and crystallization annealing temperature. Irrespective of the preparation conditions, BLT films were c-axis oriented, and had a dense surface morphology without pore to produce smooth Pt/BLT/Pt interfaces of capacitor. The film thickness was controlled as 90 nm to obtain a low coercive voltage (2V c ) without the problem of capacitor short-fail. The proper composition of Bi 3:35 La 0:85 Ti 3 O 12 was selected for the largest switching polarization (P Ã À P^), good fatigue endurance and a low leakage current density (J L ). After crystallization annealing at 700 C, the optimized film of 90 nm Bi 3:35 La 0:85 Ti 3 O 12 showed the good electrical properties, such as 2V c of 2.0 V, P Ã À P^of 13 C/cm 2 , J L of 1 Â 10 À6 A/cm 2 at a applied voltage of 3 V and no polarization loss up to 1 Â 10 11 fatigue cycles, for ferroelectric random access memory (FeRAM) application.
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