Patterned silicon substrates: A common platform for room temperature GaN and ZnO polariton lasers

Abstract

A new platform for fabricating polariton lasers operating at room temperature is introduced: nitride-based distributed Bragg reflectors epitaxially grown on patterned silicon substrates. The patterning allows for an enhanced strain relaxation thereby enabling to stack a large number of crack-free AlN/AlGaN pairs and achieve cavity quality factors of several thousands with a large spatial homogeneity. GaN and ZnO active regions are epitaxially grown thereon and the cavities are completed with top dielectric Bragg reflectors. The two structures display strong-coupling and polariton lasing at room temperature and constitute an intermediate step in the way towards integrated polariton devices.

Polariton condensation phase diagram in wide-band-gap planar microcavities: GaN versus ZnO

“…The SCR at RT was already observed and reported in these structures 36 . Here we will evidence that the SCR holds over the whole range of photonic fractions and excitation powers used in this study.…”

“…The only difference between the two cavities lies in the optical thickness of active layer: 3λ of GaN (corresponding to a physical thickness of 414 nm) or 7λ/4 of ZnO (physical thickness of 290 nm), which were both epitaxially grown on the bottom DBR by MBE too. Further details on the fabrication are given elsewhere 36 . The thicknesses of the active layer have been chosen in order to obtain a Rabi splitting 2 times larger in ZnO.…”

“…Optical cavities with large cavity quality factors in the near UV-range can be grown on silicon with high reproducibility. This progress has led to the first observation of polariton lasing at RT in bulk GaN and ZnO planar MCs on patterned silicon substrates 36 . The good optical and structural quality of the fabricated structures and their low photonic disorder now allows to carry out systematic studies of the polariton lasing threshold dependency.…”

“…In the third section, the SCR is evidenced at RT in both systems whatever the detuning and excitation power. Thanks to the low cavities photonic disorder 36 , it is also possible to study the influence of the spot size on the polariton laser threshold and the results are given and analyzed in the fourth section. Finally, a complete and detailed phase diagram is then determined for 4 the two MCs from 10 K to 300 K over a wide detuning range by using the intentional thickness gradient of the active layer across the sample, which is 2'' diameter.…”

Growth of nitride‐based light emitting diodes with a high‐reflectivity distributed Bragg reflector on mesa‐patterned silicon substrate

“…In these structures, a high reflectivity necessitates the growth of layers with a large contrast of optical index and then large lattice mismatch strain. Thanks to mesa patterns, such DBR can be grown with a strongly reduced risk of cracking [5]. Inserting a highly reflective DBR between the Si substrate and a nitride light emitting diode (LED) is particularly interesting because it can act as a reflector for the photons coming from the LED and thus enhance the total emitted optical power in the air.…”