Quantitative dopant profiling of junction in light-emitting diode using off-axis electron holography
Schematic of InGaAs LED sample structure showing Al and In compositions and nominal Si and Be concentrations. Growth direction is from left to right. Region I: Si-doped contact; region II: Si-doped barrier; region III: undoped triple QWs; region IV: Be-doped barrier; region V: Be-doped GaAs; region VI: Be-doped contact. Only the part of region I is shown in schematic.
(a) Annular-dark-field STEM cross-sectional image of InGaAs LED showing barriers and active layers. Note that the bands of darker contrast correspond to the barrier layers in regions II and IV, and lines of brighter contrast correspond to the three InGaAs QWs in region III. (b) Corresponding composition profiles, from the line indicated in (a), which confirm Al and In concentrations across entire layer sequence.
(a) Reconstructed holographic phase image of InGaAs LED. The black arrows indicate positions of three InGaAs QWs. (b) Electrostatic potential profiles , , and , from the line indicated in (a), where was extracted by subtracting from .
(a) InGaAs LED profile comparisons between experiment and simulations with and without carrier traps in AlGaAs barriers. The arrows indicate regions of discrepancy between measurement and simulation without impurities. (b) Concentration profiles of donors (region II) and acceptors (region IV) with and without carrier traps in AlGaAs barriers.
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