L. C. Luther

High-power cw vertical-cavity top surface-emitting GaAs quantum well lasers

We have devised a novel vertical‐cavity top surface‐emitting GaAs quantum well laser structure which operates at 0.84 μm. The laser combines peripheral current injection with efficient heat removal and uses only the epitaxially grown semiconductor layers for the output mirrors. The structure is obtained by a patterned deep H+ implantation and anneal cycle which maintains surface conductivity while burying a high resistance layer. Peripheral injection of current occurs from the metallized contact area into the nonimplanted nonmetallized emission window. For 10‐μm‐diam emitting windows, ∼4 mA thresholds with continuous‐wave (cw) room‐temperature output powers ≳1.5 mW are obtained. Larger diameter emitting windows have maximum cw output powers greater than 3 mW. These are the highest cw powers achieved to date in current injected vertical‐cavity surface‐emitting lasers.

Design and development of single‐layer, ion‐implantable small bubble materials for magnetic bubble devices

The general magnetic and physical requirements that a material must meet in order to be useful in magnetic bubble devices are reviewed. An approximate expression relating stripe width and film thickness to the material length parameter (l) is presented. The well‐known equations relating anisotropy, moment, Q factor and exchange constant are rearranged, and, combined with the approximate expression for l, result in a convenient set of equations which are useful for materials design and for evaluating magnetic property measurements. The exchange constant (A) of epitaxial bubble garnet films is presented as a function of Curie temperature. Nominal compositions are given in the (YLuSmCa)3(FeGe)5O12 system which will support bubble diameters from 3.0–1.7μm. The range of λ111 values which are needed to implement Ion Implanted Propagation Patterns (I2P2) is presented. An approach is presented for increasing the uniaxial anisotropy in the 〈111〉 crystallographic direction without significantly changing the damping...

Single mode magneto‐optic waveguide films

A novel triple layer film is described which provides single mode propagation in a magneto‐optically active waveguide of convenient thickness. All three layers are modified yttrium iron garnet (YIG) films grown by liquid phase epitaxy on a gadolinium gallium garnet substrate. The top film is the active layer, several microns thick. The middle layer is similar but it has a slightly smaller refractive index to assure single mode operation of the top layer. The bottom layer has high optical absorption to eliminate all of the higher order modes which are propagated in the triple layer and a slightly higher refractive index to prevent the confinement of any modes to the top two low loss layers. Using a praseodymium YIG film as the absorbing layer, 17 TE modes were propagated at 1.51 μm where the Pr absorption is low but only the TE0 mode was observed at 1.48 and 1.54 μm where the Pr absorption is high. Such triple layer garnet films will be useful in all magneto‐optic waveguide devices.

Extended temperature and wavelength performance of vertical cavity top surface emitting lasers

We report over 130 °C continuous wave operation of unbonded vertical cavity top‐surface emitting lasers emitting more than 1.0 mW at 110 °C. Furthermore, we control threshold currents to within only ±1.35 mA (±12%) over a 150 °C temperature range. We are also able to control the threshold current to within a factor of 2 over a 50 nm wavelength range using the same epidesign.

An improved BiYIG composition for one‐micron bubbles

Robertson et al.1 have described a Ga‐substituted BiYLuIG composition with very narrow linewidth, high Faraday contrast, and low coercivity. In this work, the temperature dependence of magnetic properties has been improved by replacement of the Ga in the above material by Ca,Si. The approximate composition of the improved material is Y1.9Bi0.5Ca0.6Fe4.4Si0.6O12, and it has a 4πM of 800 G at RT. The Curie temperature is 525 °K higher than that of the Ga‐substituted equivalent. An anisotropy energy of 75 000 erg/cm3 and a stability factor Q of 3.8 have been measured. The temperature dependence of the collapse field was reduced from −0.35% to −0.22% per degree. The magnetostrictive coefficient λ111 was measured and used to estimate strain corrections to the anisotropy energy. The growth‐induced anisotropy was correlated with Bi content. The Faraday rotation was measured at RT and at 1.4 °K over the range (1.5–2)×104 cm−1. In triply implanted films, bubble propagation has been observed on 4‐μm period Ion Impl...

Low‐threshold GaAs/AlGaAs quantum‐well lasers grown by organometallic vapor‐phase epitaxy using trimethylamine alane

We have utilized a new aluminum source, trimethylamine alane (TMAA), in the growth of graded‐index separate‐confinement heterostructure single quantum‐well GaAs/AlGaAs laser structures by low pressure (30 Torr) organometallic vapor‐phase epitaxy. We find lower carbon and oxygen incorporation in AlGaAs epilayers using TMAA since it does not contain a direct Al–C bond and it is not susceptible to the formation of volatile Al–O containing compounds. The oxygen and carbon concentrations were below the detection limits (< 5 × 1016 cm−3 and < 3 × 1016 cm−3, respectively) of the secondary ion mass spectrometry measurements. Broad‐area lasers with 10‐nm quantum wells and Al0.45Ga0.55As cladding layers exhibited threshold current densities of 140 A cm−2 for cavity lengths of 1 mm, internal quantum efficiencies of 81%, and intrinsic losses of 1.6 cm−1. These results demonstrate that extremely high‐quality AlGaAs and GaAs quantum wells can be grown with TMAA.

Growth‐induced anisotropy and damping versus temperature in narrow linewidth, 1‐μm YIG(Bi, Ca, Si) bubble films

The variation of growth‐induced anisotropy Ku and damping with temperature are reported in 1‐μm films of (YBiCa)3(FeSi)5O12 having very narrow FMR linewidths. In contrast to a more conventional Lu‐Sm type 1‐μm bubble film, Ku is found to vary much more slowly with temperature (approximately as M2) in the Bi‐containing film with no magnetic rare earths. Also, the important bubble parameter Δl/ΔT, where l is the material length, is found to be smaller than that of the Lu‐Sm type material and of opposite sign. Significant improvements in device temperature stability and operating speeds are expected in the YIG(Bi) system.

Carbon‐doped long wavelength GaAs/AlxGa1−xAs quantum well infrared photodetectors grown by organometallic vapor phase epitaxy

We report p‐doped long wavelength GaAs/AlxGa1−xAs quantum well infrared photodetectors (QWIP) grown by organometallic vapor phase epitaxy. The operation of these devices is based on the photocurrent induced through valence‐band intersubband absorption by holes and, unlike n‐doped QWIPs, can utilize normal incidence illumination. Carbon was used as the p‐type dopant in a low‐pressure (30 Torr) vertical‐geometry reactor. The C‐doped QWIPs consisted of fifty periods of 54‐nm‐thick undoped AlxGa1−xAs (x=0.36 or 0.30) and C‐doped GaAs wells (Lz=4 or 5 nm). Using normal incidence illumination, the C‐doped QWIP with shorter wavelength response (x=0.36, Lz=4 nm) exhibited a quantum efficiency of η=21.4% and a detectivity at the peak wavelength of Dλ=5.4×109 cm √Hz/W at 77 K. The peak and cutoff wavelengths were λp=8.1 μm and λco=8.9 μm, respectively. The C‐doped QWIP with longer wavelength response (x=0.30, Lz=5 nm) exhibited a normal incidence η=22.1% and Dλ*=3.5×108 cm √Hz/W for λp=10.5 μm (λco=11.7 μm). The de...

Unintentional zinc diffusion in InP pn-homojunctions

Unintentional zinc diffusion into uniformly Si-doped InP layers has been studied. The sharp non-error function Zn concentration profiles and inflections are shown to be consistent with the substitutional-interstitial mechanism when the influence of the electrostatic field of the pn-junction on diffusion is taken into consideration.

Large growth‐induced anisotropy to preferential occupation of the iron sites in garnets

Large growth‐induced anisotropies (Ku) arising from the preferential occupation of Ir4+ on octahedral sites have been measured. For YIG with approximately 0.2 Ir atoms per garnet formula unit and Mg2+ as a charge compensator, values of Ku=+4.5×105 ergs/cm3 have been obtained. The induced anisotropy is proportional to the Ir4+ present as deduced from the optical absorption.