The metalorganic chemical vapor deposition (MOCVD) of epitaxial III‐V semiconductor alloys on III‐V substrates is reviewed in detail. The emphasis is placed on both practical and theoretical knowledge of the equipment and deposition process. The chemistry of the source alkyls and the dynamics of the transport process are discussed. The growth of the GaAs and AlxGa1−xAs systems are treated as prototypical examples (and the most studied) of the III‐V materials. Latter sections review InP, Ga1−xInxAs, and related alloys. Finally, the antimonide and the other systems are reviewed. Electronic and optical devices fabricated from MOCVD‐grown materials are used as examples of the capabilities of the growth technique.

Metalorganic chemical vapor deposition of III‐V semiconductors

The fabrication of GaSb infrared‐sensitive photovoltaic cells designed to boost the energy‐conversion efficiency in tandem solar cell stacks is reported. Located behind GaAs solar‐cells in 50× concentrated light configurations, these GaSb cells will boost the stack efficiency by 6.5 percentage points for space (AM0) and 7.0 percentage points for terrestrial (AM1.5D) applications. Assuming a GaAs cell efficiency of 26.7% (AM1.5D, 50×) as recently reported, the GaAs on GaSb stack efficiency will be 33.7%. Reduced series resistance in future GaSb cells will allow tandem‐stack energy‐conversion efficiencies over 35%.

GaSb booster cells for over 30% efficient solar‐cell stacks

A laser diode assembly provides multiple output beams from multiple p-n junctions in a multiplicity of stacked laser diodes with at least one tunnel junction. A semiconductor substrate has a multiplicity of superposed semiconductor laser stacks thereon each having an active layer sandwiched between p and n layers, and at least one pair of adjacent semiconductor laser stacks has a tunnel junction therebetween. When a potential is applied across the ohmic contacts on the outer surface of the substrate and the outer surface of the uppermost semiconductor laser stack, lasing is produced in the semiconductor stacks to form multiple beams. The tunnel junction may be provided by highly doped p + , n + layers between the stacks, or it may be provided by highly doped abutting p + , n + surface portions in the adjacent stacks. Tunnel junctions may be provided at the interfaces between all of the stacks, or between all but one pair of the adjacent stacks. The assembly may be edge emitting or surface emitting, and it may include single or multiple quantum well configurations and distributed feedback configuration.

Laser diode assembly with tunnel junctions and providing multiple beams

Metal-organic vapor phase epitaxy of compound semiconductors

An inverted metamorphic multifunction solar cell, and its method of fabrication, including an upper subcell, a middle subcell, and a lower subcell, including providing a first substrate for the epitaxial growth of semiconductor material; forming an upper first solar subcell on the substrate having a first bandgap; forming a middle second solar subcell over the first solar subcell having a second bandgap smaller than the first bandgap; forming a graded interlayer over the second subcell, the graded interlayer having a third bandgap greater than the second bandgap; and forming a lower third solar subcell over the graded interlayer having a fourth bandgap smaller than the second bandgap such that the third subcell is lattice mismatched with respect to the second subcell, wherein at least one of the solar subcells has heterojunction base-emitter layers.

Heterojunction subcells in inverted metamorphic multijunction solar cells

GaAs space solar cells with areas of 4 cm2 have been fabricated by metalorganic chemical vapor deposition. The AlGaAs‐GaAs heteroface structures have been grown in both the p‐n and n‐p configurations. Under one sun, air mass zero conditions and at 25 °C, the p‐n cell is characterized by a short‐circuit current density of 32.3 mA/cm2, an open‐circuit voltage of 1.05 V, and a fill factor of 0.84, resulting in a conversion efficiency of 21.1%. The corresponding values for n‐p cells are 33.8 mA/cm2, 1.01 V, and 0.83, resulting in a conversion efficiency of 21.0%.

21 % (one sun, air mass zero) 4 cm2 GaAs space solar cells

The crystallographic connection of MOCVD-grown monolithic cascade subcells via transparent graded layers

Magnesium has been substituted for zinc in GaAs and Ga(0.75)In(0.25)As solar cells grown by metalorganic chemical vapor deposition (MOCVD). Bis(cyclopentadienyl)magnesium (Cp2Mg) is used as the MOCVD transport agent for Mg. Full retention of excellent material quality and efficient cell performance results. The substitution of Mg for Zn would enhance the abruptness and reproducibility of doping profiles, and facilitate high temperature processing and operation, due to the much lower diffusion coefficient of Mg, relative to Zn, in these materials.

C. W. Ford

Papers

21 % (one sun, air mass zero) 4 cm2 GaAs space solar cells

The crystallographic connection of MOCVD-grown monolithic cascade subcells via transparent graded layers

Magnesium doping of efficient GaAs and Ga(0.75)In(0.25)As solar cells grown by metalorganic chemical vapor deposition

A two-terminal, two-junction monolithic cascade solar cell in a lattice-mismatched system

Reproducible integration of multijunction cascade cell components