(Color online) Band diagrams of the conduction band (upper) and valence band (lower) of the design of Barbieri et al. 11 On the upper pane the lower (red), injector (green), and upper (blue) levels are indicated. On the lower pane the heavy hole states only are shown, the heavy hole ground state for each period is shown in black. A field of 2.3 is applied.
(Color online) Energy difference between the heavy hole ground state and the electronic states as a function of applied electric field. The state with the largest overlap with the heavy hole ground state is marked with large dots (red), at higher fields this state is the lower laser level. The upper laser level is marked with large squares (blue), other states are shown gray. For some fields data is missing as the solver did not converge at these fields.
(Color online) IV taken at 10 K plotted with the corresponding differential resistance. The dashed lines indicate the threshold current, when maximum power is achieved and laser shut-off. The IV was taken in DC with a Keithley 2400 SMU.
(Color online) The PL spectra of the homogeneous device at applied voltages between 0 and 4 V. The white dashed lines correspond to laser threshold, maximum optical power, and laser shut-off. Each spectrum has been normalized to the main PL peak.
(Color online) The PL spectra obtained at four different applied biases. The data have been fitted with a number of peaks in each case.
(Color online) Fitting parameters as a function of applied bias. The black marks show the energy difference between the “upper” and “lower” states in THz. The red marks show the magnitude of the “upper” level relative to the main PL peak. The dashed lines indicate the laser threshold, maximum power and shut-off.
The spectra obtained from wafer V564 as a function of current. The dashed lines mark the different emission regimes, labeled (i), (ii), and (iii).
(Color online) The IV and differential resistance from the multi-frequency device. The black line is the IV (left scale) and the red curve is the differential resistance (right scale). The dashed lines mark the different emission regimes, labeled (i), (ii), and (iii).
(Color online) Results from PL obtained from (a) sub-stack “A” (top) and (b) “B” (bottom). The energy separation of the “lower” and “upper” states (black marks, left scale) and the relative magnitude of the “upper” state (blue marks, right scale) are shown as a function of applied bias.
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