In recent years, thin-film photovoltaic (PV) companies started realizing their low manufacturing cost potential, and
grabbing an increasingly larger market share from multicrystalline silicon companies. Copper Indium Gallium Selenide
(CIGS) is the most promising thin-film PV material, having demonstrated the highest energy conversion efficiency in
both cells and modules. However, most CIGS manufacturers still face the challenge of delivering a reliable and rapid
manufacturing process that can scale effectively and deliver on the promise of this material system. HelioVolt has
developed a reactive transfer process for CIGS absorber formation that has the benefits of good compositional control,
high-quality CIGS grains, and a fast reaction. The reactive transfer process is a two stage CIGS fabrication method.
Precursor films are deposited onto substrates and reusable print plates in the first stage, while in the second stage, the
CIGS layer is formed by rapid heating with Se confinement. High quality CIGS films with large grains were produced
on a full-scale manufacturing line, and resulted in high-efficiency large-form-factor modules. With 14% cell efficiency
and 12% module efficiency, HelioVolt started to commercialize the process on its first production line with 20 MW
An all-epitaxial process is described for obtaining an intracavity aperture in GaAs-based vertical-cavity surface-emitting lasers (VCSELs) that lead to simultaneous current and optical confinement. The laser structure starts with 30 pairs of n-type GaAs/AlAs bottom DBR mirrors, a full-wave cavity including three 6nm In0.2Ga0.8As quantum wells at the center, and 1.5 pairs of p-type GaAs/AlGaAs DBR mirrors. A tunnel junction is deposited thereafter, which includes AlGaAs etch-stop, 30nm p+ (Be = 5×1019 cm-3) GaAs, 10nm n+ (Si = 5×1019 cm-3) In0.1Ga0.9As, and 30nm n+ (Si = 1×1019 cm-3) GaAs. Apertures are defined by removal of the tunnel junction layers outside the aperture via ex-situ lithography and wet etching. The VCSEL structure is completed by an MBE regrowth of 15 pairs of n-type GaAs/AlAs DBRs. Simple post-grown processing includes metal ring contact deposition and device isolation (wet-etching through the cavity.) The current confinement in the area far from the aperture is shown to be excellent from the measurement of the same-size dummy mesas and metal contacts next to the working devices on the same wafer. At room temperature, a 10 μm circular-aperture VCSEL lases under pulsed current injection with a threshold current of 2.6mA. Some limitations in the continuous wave operating characteristics will be described and are believed to arise from Be diffusion. Replacing Be with a less diffusive C dopant can greatly improve the device performance.