Quantum-well AlxGa1 - xAs-GaAs heterostructure lasers grown by metalorganic chemical vapor deposition

Data are presented on photopumped single- and multiple-quantum-well Al
x
Ga
1-x
As-GaAs heterostructures grown by metalorganic chemical vapor deposition (MO-CVD) showing that continuous room-temperature (CW 300 K) laser operation of such structures is possible in the range 0-150 meV above the GaAs active region band edge (
\Delta E \equiv \hbar \omega - E_{g} = 0-150
meV). Optically pumped multiple-quantum-well heterostructure lasers of short cavity length (
l \lsim 20 \mu
m), and thus high edge-to-edge cavity end losses, are shown to operate at photo-excitation threshold levels as low as 900 W/cm
²
(
J_{th} \sim 375
A/cm
²
). As the quantum-well dimension is reduced to
L_{z} \lsim 100
Å, single-active-layer heterostructures shift their laser operation to higher confined-particle states, or fail to operate altogether, whereas multiple-active-layer heterostructures continue to operate as lasers on the lowest confined-particle states
n = 1 e \rightarrow hh
and
n' = 1' e \rightarrow lh
transitions). For a multiple-quantum-well heterostructure of small enough GaAs active region size,
L_{z} < 80
Å, recombination radiation at the energy gap is cut off, and as expected, laser operation on the lowest confined-particle states (1 - 1') is shifted to high energy (
\hbar \omega - E_{g} > 50
meV).