H. F. Chung

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.

Stability of 300 K continuous operation of p‐n AlxGa1−xAs‐GaAs quantum well lasers grown on Si

Data are presented on p‐n (diode) AlxGa1−xAs‐GaAs quantum well lasers grown on Si indicating that continuous 300 K operation is possible for four or more hours. Lower threshold diodes (1.4 kA/cm2) of given dislocation density are not necessarily as stable as higher threshold diodes (1.8 kA/cm2) of lower dislocation density, ∼10 min vs ≳4 h. Stability data on diodes agree with the behavior of photopumped samples of the same crystals with the Si substrates removed.

Unified planar process for fabricating heterojunction bipolar transistors and buried‐heterostructure lasers utilizing impurity‐induced disordering

We describe results on a novel geometry of heterojunction bipolar transistor that has been realized by impurity‐induced disordering. This structure is fabricated by a method that is compatible with techniques for the fabrication of low threshold current buried‐heterostructure lasers. We have demonstrated this compatibility by fabricating a hybrid laser/transistor structure that operates as a laser with a threshold current of 6 mA at room temperature, and as a transistor with a current gain of 5.

AlGaAs multiple-wavelength light-emitting bar grown by laser-assisted metalorganic chemical vapor deposition

The first optical device fabricated from epitaxial material grown by laser‐assisted crystal growth is reported. The device is an AlGaAs multiple‐wavelength light‐emitting bar in which the Al composition of the active layer, and thus the emission wavelength, varies as a function of position along the bar. The Al composition is photochemically patterned during growth with an in situ Ar+ laser beam. The energy band gap increases from a minimum of 1.475 eV to a maximum of 1.52 eV over a 4 mm section of the bar. The spatial dependence of the energy band gap is roughly Gaussian and corresponds to the laser intensity profile. The electroluminescent data are presented along with a brief discussion of the laser‐assisted crystal growth process.

Demonstration and properties of a planar heterojunction bipolar transistor with lateral current flow

The authors present fabrication techniques and device performance for a novel transistor structure, the lateral heterojunction bipolar transistor. The lateral heterojunctions are formed by impurity-induced disordering of a GaAs base layer sandwiched between two AlGaAs layers. These transistor structures exhibit current gains of 14 for base widths of 0.74 mu m. Transistor action in this device occurs parallel to the surface of the device structure. The active base region of the structure is completely submerged, resulting in a reduction of surface recombination as a mechanism for gain reduction in the device. Impurity-induced disordering is used to widen the bandgap of the alloy in the emitter and collector, resulting in an improvement of the emitter injection efficiency. Since the device is based entirely on a surface diffusion process, the device is completely planar and has no steps involving etching of the III-V alloy material. These advantages lead this device to be considered as a candidate for optoelectronic integration applications. The transistor device functions as a buried heterostructure laser, with a threshold current as low as 6 mA for a 1.4- mu m stripe. >

Continuous (300 K) photopumped laser operation of AlxGa1−xAs‐GaAs quantum well heterostructures grown on strained‐layer GaAs on Si

Data are presented demonstrating continuous (cw) room‐temperature photopumped laser operation of an AlxGa1−xAs‐GaAs quantum well heterostructure (QWH) grown on a Si substrate. The QWH is grown in a two‐step process with first the GaAs grown on the Si substrate by molecular beam epitaxy (MBE) and second the QWH grown by metalorganic chemical vapor deposition (MOCVD). The MBE GaAs contains a thin 600‐A layer at the Si/GaAs interface that is rich in defects, ‘‘absorbs’’ much of the mismatch, and provides a good surface (specular surface) for the MOCVD growth of the QWH. Although cw 300 K laser operation is obtained, it occurs at high threshold and is short lived, agreeing with earlier results on the cw 300 K laser operation of mismatched III‐V QWH’s.

Surface skimming buried heterostructure laser with applications to optoelectronic integration

We demonstrate the ability to fabricate low‐threshold current buried heterostructure lasers with the critical active layers in close proximity to the surface of the laser crystal. These structures readily lend themselves to applications involving optical field interactions on the surface of the crystal. We further demonstrate the compatibility of these structures with lateral heterojunction bipolar transistor fabrication.

In situ laser patterned desorption of GaAs quantum wells for monolithic multiple wavelength diode lasers

A new laser‐assisted crystal growth technique that enables three‐dimensional patterning of the GaAs quantum well (QW) active layer within a laser diode structure is demonstrated. In this technique, the GaAs QW is locally heated with superimposed Ar+ and Nd:YAG laser beams during a pause in the metalorganic chemical vapor deposition growth. The evaporation rate of the GaAs is greatly increased by the laser heating, locally thinning the QW. After exposure, the crystal growth is resumed, burying the patterned QW within the crystal. Transmission electron microscopy is used to quantify the lateral profile of the QW thickness while photoluminescence is used to demonstrate the spatial variation of the energy band gap. Finally, multiple wavelength operation of broad‐area diode lasers is observed, consistent with the spatial variation in the energy band gap.

Low threshold current dual wavelength planar buried heterostructure lasers with close spatial and large spectral separation

A novel technique for achieving closely spaced laser devices with large, but well‐controlled, wavelength separation is described. Preferential population of the lowest band‐gap active region in a stacked active layer structure is used along with patterned etching of the long wavelength active regions and regrowth over all devices to achieve the desired wavelength. Dual‐wavelength dual‐stripe buried heterostructure lasers with 5 μm stripes on 20 μm centers formed by impurity‐induced layer disordering in a stacked active layer structure have threshold currents of 9.1 and 10.9 mA for laser wavelengths of 846 and 760 nm, respectively.

Achievement of high gain in a multiple quantum channel lateral heterojunction bipolar transistor

We describe refinements in the geometry of a lateral heterojunction bipolar transistor that have allowed us to greatly improve the dc characteristics of these devices. By reducing the base dimensions to 0.35 μm and improving the abruptness of the grading at the base‐emitter p‐n junction, we have achieved maximum current gains in excess of 600.