Harry Lee

Monolithic integration of room-temperature cw GaAs/AlGaAs lasers on Si substrates via relaxed graded GeSi buffer layers

GaAs/AlxGa(1−x)As quantum well lasers have been demonstrated via organometallic chemical vapor deposition on relaxed graded Ge/GexSi(1−x) virtual substrates on Si. A number of GaAs/Ge/Si integration issues including Ge autodoping behavior in GaAs, reduced critical thickness due to thermal expansion mismatch, and complications with mirror facet cleaving have been overcome. Despite unoptimized laser structures with high series resistance and large threshold current densities, surface threading dislocation densities for GaAs/AlGaAs lasers on Si substrates as low as 2×106 cm−2 permitted continuous room-temperature lasing at a wavelength of 858 nm. The laser structures are uncoated edge-emitting broad-area devices with differential quantum efficiencies of 0.24 and threshold current densities of 577 A/cm2. Identical devices grown on commercial GaAs substrates showed similar behavior. This comparative data agrees with previous measurements of near-bulk minority carrier lifetimes in GaAs grown on Ge/GeSi/Si subst...

Dispersion of Ceramic Particles in Organic Liquids

Good dispersion of oxide ceramics in organic solvents can be achieved using many different dispersants. Several types of dispersants, including fatty acids, coupling agents, polar aromatic compounds and polymers, are discussed to illustrate the important phenomena. Many new problems arise in actual slips during ceramics processing; these are briefly discussed.

Strategies For Direct Monolithic Integration of AlxGa(1-x)As/InxGa(1-x)As LEDS and Lasers On Ge/GeSi/Si Substrates Via Relaxed Graded GexSi(1-x) Buffer Layers

Abstract : Al(x)Ga(1-x)As/GaAs quantum well lasers have been demonstrated via organometallic chemical vapor deposition (OMCVD) on relaxed graded Ge/Ge(x)Si(1-x) virtual substrates on Si. Despite Un-optimized laser structures with high series resistance and large threshold current densities, surface threading dislocation densities as low as 2 x 10(exp 6)/sq cm enabled cw room-temperature lasing at a wavelength of 858 nm. The laser structures are oxide-stripe gain-guided devices with differential quantum efficiencies of 0.16 and threshold current densities of 1550A/sq cm. Identical devices grown on commercial GaAs substrates showed differential quantum efficiencies of 0.14 and threshold current densities of 1700A/sq cm. This comparative data agrees with our previous measurements of near-bulk minority carrier lifetimes in GaAs grown on Ge/GeSi/Si substrates. A number of GaAs/Ge/Si integration issues including thermal expansion mismatch and Ge autodoping behavior in GaAs were overcome.

Large core polymer waveguides for optical backplanes in microfluidic systems

A platform is developed which utilizes polymer materials used for the chips to create waveguide based optical components. With the fabrication method demonstrated, waveguides, power splitters, combiners and bends can be introduced and integrated cheaply into existing biochips