G. S. Jackson

Room‐temperature continuous operation of p‐n AlxGa1−xAs‐GaAs quantum well heterostructure lasers grown on Si

We describe the construction and room‐temperature (300 K) continuous (cw) operation of p‐n diode Al x Ga1−x As‐GaAs quantum wellheterostructure (QWH) lasers grown on Si substrates. The QWH crystal is grown in two stages, the first part by molecular beam epitaxy(MBE) and the single‐well quantum well active region by metalorganic chemical vapor deposition(MOCVD). Simple gain‐guided stripe configuration lasers fabricated on the MBEMOCVD QWH wafer operate cw at 300 K and have pulsed thresholds as low as 1.8×103 A/cm2.

Carbon‐doped AlxGa1−xAs‐GaAs quantum well lasers

Data are presented demonstrating that carbon (C) can be used as the active p‐type dopant in high‐quality AlxGa1−xAs‐GaAs quantum well laser crystals. We show, by fabricating three different types of stripe geometry laser diodes (oxide stripe, hydrogenated stripe, and impurity‐induced layer‐disordered stripe), that C is a stable dopant and compatible in behavior with typical integrated‐circuit style of device processing. The data suggest that more complicated laser geometries are possible on C‐doped material because of minimal pattern ‘‘undercutting’’ after processing by, for example, hydrogenation or impurity‐induced layer disordering.

Stripe‐geometry AlxGa1−xAs‐GaAs quantum well lasers via hydrogenation

Data are presented on stripe‐geometry gain‐guided AlxGa1−xAs‐GaAs quantum well heterostructure lasers fabricated via masked (SiO2) hydrogen compensation (‘‘hydrogenation’’) of the Mg and Se dopants in the multiple layer heterostructure. Continuous room‐temperature laser operation is achieved with a threshold current of 24 mA and 24 mW total output at 50 mA. Near‐field emission patterns show strong current confinement in the stripe‐active region, and significant hydrogenation ‘‘undercutting’’ of the oxide mask.

Coupled stripe AlxGa1−xAs‐GaAs quantum well lasers defined by impurity‐induced (Si) layer disordering

A high‐performance index‐guided ten‐stripe AlxGa1−xAs‐GaAs quantum well heterostructure laser array fabricated using Si diffusion to effect impurity‐induced layer disordering between the active region stripes is described. The fine spacing (1 μm) between (3 μm) emitters allows coupled mode laser operation at thresholds (Ith) as low as 3–4 mA per stripe and with stable near‐ and far‐field patterns in spite of band filling (single quantum well). This form of coupled stripe laser is capable of high efficiency and high power output (250 mW at 300 mA) as well as a large excitation range extending from Ith to 9Ith.

High‐power gain‐guided coupled‐stripe quantum well laser array by hydrogenation

High‐power coupled‐stripe (ten‐stripe) AlxGa1−xAs‐GaAs quantum well lasers that are fabricated by hydrogenation are described. Continuous (cw) room‐temperature thresholds as low as Ith=90 mA and internal quantum efficiency as high as 85% are demonstrated. Continuous 300 K laser operation generating 2×375 mW (0.75 W) at 910 mA (10Ith) or 57% efficiency is described (8‐μm‐wide stripes on 12 μm centers). Minimal heating effects are observed up to the point of catastrophic failure.

Coupled‐stripe AlxGa1−xAs‐GaAs quantum well lasers defined by vacancy‐enhanced impurity‐induced layer disordering from (Si2)y(GaAs)1−y barriers

Data are presented showing that high‐performance (>100 mW) AlxGa1−xAs‐GaAs quantum well heterostructure (QWH) coupled‐stripe laser arrays can be realized by vacancy‐enhanced impurity‐induced layer disordering (IILD) employing an internal (Si2)y(GaAs)1−y barrier. This form of Si IILD (i.e., layer disordering from a ‘‘finite’’ internal Si source) results in coupled‐emitter laser operation, even for relatively large stripe (7–10 μm) and spacing dimensions (2 μm), at currents just above threshold and higher. As a separate issue, the Si IILD QWH laser cross sections show that Si diffusion from a surface source is ‘‘slower’’ than the simultaneous vacancy diffusion from an SiO2 surface encapsulant (‘‘cap’’).

Impurity‐induced layer‐disordered buried heterostructure AlxGa1−xAs‐GaAs quantum well edge‐injection laser array

A laser array is described that makes use of edge injection into two sides (two ‘‘edges’’) of a stack of three AlxGa1−xAs‐GaAs multiple quantum well active regions. The edge‐injection array is realized by impurity‐induced layer disordering, which forms a higher gap Si‐doped n‐type emitter that edge injects electrons into either side of a stack of three lower gap multiple quantum well p‐type active regions. The far‐field beam divergence in the vertical direction (θ⊥) of the array diode is reduced from 45° to 15° as determined by the laser operation, for comparison, of one of the quantum well active regions (oxide‐defined stripe geometry diode).

Index‐guided AlxGa1−xAs‐GaAs quantum well heterostructure lasers fabricated by vacancy‐enhanced impurity‐induced layer disordering from an internal (Si2)y(GaAs)1−y source

A unique form of Si impurity‐induced layer disordering (Si IILD) is described that utilizes a ‘‘buried’’ Si source, a (Si2)y(GaAs)1−y barrier, and a patterned external source of column III vacancies, an SiO2 cap, to define the layer disordering. This form of Si IILD is used to fabricate stripe‐geometry index‐guided laser diodes that are capable of kink‐free single‐mode operation.

Broadband operation of coupled-stripe multiple quantum well AlGaAs laser diodes

A recently developed AlGaAs multiple stripe, multiple quantum well superluminescence light‐emitting diode (SLED) with an extremely low reflectivity front‐facet coating is operated as a high‐power laser in an external grating cavity over an unusually broad tuning range. The SLED diode is operated continuously (cw) in a tuning range Δℏω∼94 meV and a power output from the grating cavity of 75 mW (optical flux ∼500 mW within the compound cavity). Data are presented showing the output power as a function of wavelength at currents of 750 mA (7660 A<λ<8040 A) and 1.0 A (7620 A<λ<8085 A). The threshold current in pulsed laser operation is measured over a range of 130 meV.

Damaged and damage‐free hydrogenation of GaAs: The effect of reactor geometry

The effects on GaAs hydrogenation of two different rf reactor types are investigated, one a parallel‐plate reactor with a capacitively coupled discharge and the other an inductively coupled system. The atomic hydrogen, dissociated in the plasma of either system, passivates impurities in GaAs. The plasma in the capacitively coupled discharge reactor develops a large self‐bias relative to the sample and large ion energies (∼100 eV), resulting in significant etching of the GaAs surface. In spite of the surface erosion, passivation of donors by hydrogen diffusing into the material is observed. The sample hydrogenated in the inductively coupled discharge (kTe/q <1–2 eV) is not etched, exhibiting, nevertheless, a comparable passivation of donors. Hydrogenation without surface damage is accomplished with the sample in the glow discharge of an inductively coupled reactor but not in a capacitively coupled discharge.