Investigations on Al$_{\bm x}$Ga $_{\bm {1-x}}$As Solar Cells Grown by MOVPE

Solar cells based on Al
_x
Ga
_1-x
As in its direct bandgap range were fabricated and analyzed. We show that state-of-the-art metalorganic vapor phase epitaxy systems and precursors are capable of growing Al
_x
Ga
_1-x
As solar cells with defect concentrations up to 1 × 10
¹⁴
cm
^-3
and less determined by deep level transient spectroscopy. However, for the n-doped material, inevitable DX-centers exist. These dopant-related defects limit the performance of the investigated Al
_x
Ga
_1-x
As solar cells with x ≥ 0.20. To overcome this issue, the n-doped Al
_x
Ga
_1-x
As As emitter can be replaced by an n-doped Ga
_0.51
In
_0.49
P heteroemitter. This heterojunction solar cell again shows overall defect concentrations below 1 × 10
¹⁴
cm
^-3
and significantly improved cell characteristics.