Abstract
Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm2 above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers.
Highlights
Growth of single-crystal silicon carbide on silicon substrate (SiC-on-Si) is seen as a very attractive approach to combine the excellent properties of SiC with the low cost, large wafer size and well-developed micro-machining of Si wafers
Monolithic growth of a distributed Bragg reflectors (DBRs) for gallium nitride based (GaN) devices on Si requires the use of transparent materials which are compatible with both Si and III-N semiconductors, strongly limiting the number of suitable candidates
The DBR structure using Si-doped AlGaN shows very good vertical electrical conductivity, with current density as high as 70 A/cm[2] at 1.5 V, without visible degradation of the optical performance compared to its non-conductive counterpart
Summary
David Massoubre[1], Li Wang[1], Leonie Hold[1], Alanna Fernandes[2], Jessica Chai[1], Sima Dimitrijev1 & Alan Iacopi[1]. It is worth noting that thanks to their large stop-band, mismatch between the peak reflectance of a SiC-based DBRs and the LED light emission, often unavoidable with non-uniform growth, is less critical than with DBRs with much smaller stop-band as typically obtained with III-N DBRs. Vertical electrical conductivity of the SiC-based DBRs was measured. Furthemore, high vertical conductivity was demonstrated with a measured current density of 70 A/cm[2] for an applied bias of just 1.5 V, without optical degradation compared to a non-conductive SiC/AlN DBR counterpart Those results show that single-crystal doped SiC/ AlGaN DBR with high RI contrast, high electrical conductivity and high expected thermal conductance is a promising photonic structure for the large-scale integration of SiC and GaN-based visible optoelectronic devices on Si wafer, as well as for the development of optical micro-cavity devices on Si substrate
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