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Growth and Optimisation of Ga(N,As,P,Sb)/(B,Ga)(As,P) Heterostructures for Laser Applications on Si(001)
During the past years the field of photonic integrated circuits has gained increased attention by the scientific and industrial community. The integration of photonic devices into the existing CMOS technology (complementary metal-oxide-semiconductor), i.e. Si chip manufacturing, offers a lot of room...
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| Format: | Doctoral Thesis |
| Language: | English |
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Philipps-Universität Marburg
2022
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| Online Access: | PDF Full Text |
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| Summary: | During the past years the field of photonic integrated circuits has gained increased attention by the scientific and industrial community. The integration of photonic devices into the existing CMOS technology (complementary metal-oxide-semiconductor), i.e. Si chip manufacturing, offers a lot of room for improvement concerning data transmission towards high bandwidth density, but also in the field of gas sensing or biomedical applications as affordable and wearable, small chip-sized devices. Especially in the field of data transmission, efficient and reliable laser light sources are required in the near infrared spectral range. Due to the lack of efficient Si-based light sources, the integration of a laser on CMOS compatible Si(001) 300 mm wafers, which are standardized in silicon industry, remains a large challenge up to date. This work aims to realize lasers grown lattice matched on exactly oriented Si(001) substrates via metalorganic vapour phase epitaxy (MOVPE). Therefore, the optimization of Ga(N,As,P,Sb)/(B,Ga)(As,P) heterostructures is pursued for the goal of room temperature lasing. This includes the MOVPE growth of the heterostructures themselves, their characterization via high resolution X-ray diffractometry (HR-XRD), atomic force microscopy (AFM), electrochemical capacitance-voltage profiling (ECV) and photoluminescence spectroscopy (PL). Broad area laser structures are processed for electrically pumped lateral carrier injection geometries as required for on-chip devices. Laser structures are characterized via electroluminescence spectroscopy (EL). The lattice matched bulk layers of realized electroluminescence devices consist of the indirect band gap semiconductor (B,Ga)(As,P). In investigated devices (B,Ga)(As,P) layers lead to an increased onset voltage as well as differential resistance compared to well established materials such as GaAs in established devices. In this work the (B,Ga)(As,P) material system is extensively investigated in terms of growth conditions and doping in order to optimize the layers for laser applications. A significant reduction of the onset voltage from 4.5(1.5) V down to 1.6(1) V is achieved. This improvement is associated with large reductions of energy and heat dissipation of the devices which makes them electrically competitive to industrially established laser devices on other substrates. The optically active Ga(N,As,P,Sb) quantum well (QW) layers are grown under various MOVPE conditions and improved towards smooth interfaces with the surrounding barriers and stronger luminescence. Extended defect, that form mainly during the overgrowth of modulated upper QW interfaces, become visible in AFM topographies due to the formation of 3 dimensional platelets on the heterostructures surfaces. At 575°C growth temperature Ga(N,As,Sb) was optimized in which Sb is assumed to mainly act as a surfactant. Test structures that contain about 9.5% N in the QW are found to result in low defect formation during overgrowth compared to Sb-free structures while also resulting in high optical output powers in PL- as well as EL-structures. At about 11% N the test structures surface roughness, i.e. of overgrown QWs, could be reduced down to about 0.25 nm RMS roughness in AFM topography scans and the platelet formation was completely suppressed. The optical output power of structures containing 11% N and more reduces compared to those containing 9.5% N despite the smoother interfaces which is likely caused by non-radiative recombination from N related states like N-chains or N-cluster configurations in the QWs. Unsymmetrical di-methylhydrazine (UDMHy), a standard MOVPE precursor for nitrogen incorporation, as well as the novel N-As precursor ditertiarybutylaminoarsane (DTBAA) are compared in detail for the growth of Ga(N,As,P) QW layers. Nearly comparable optical output power of electroluminescence structures is realized using DTBAA as N-precursor showing its great potential due to the high N-incorporation efficiency. Furthermore, fundamental research is provided concerning the growth of Ga(N,P) and Ga(N,As,P) layers grown lattice matched to Si(001), of Ga(P,Sb) QW layers and their investigation towards a potential direct band gap, and of high Sb-containing Ga(P,Sb) quantum dots (QDs) on the same substrates. |
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| DOI: | 10.17192/z2023.0218 |