Reflectance anisotropy spectroscopy assessment of the MOVPE nucleation of GaInP on germanium (1 0 0)

Barrigón, Enrique; Galiana, B.; Rey‐Stolle, Ignacio

doi:10.1016/j.jcrysgro.2010.09.038

Cited by 23 publications

(24 citation statements)

References 16 publications

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“…Two different growth temperatures (640 and 675°C) were used to grow these III‐V layers, to test their effects on the emitter formation and its performance, and the growth time was around 45 minutes in all cases. Details on the growth can be found elsewhere …”

Section: Experimental and Modellingmentioning

confidence: 99%

“…Details on the growth can be found elsewhere. 4 Triple junction solar cell solar cells were also grown by using the same nucleation conditions (materials, growth temperature, and Ge wafer resistivity). Table 1 includes information about the growth temperatures and time employed during the growth of the 3JSCs, and more generic details about these 3JSC structures can be found elsewhere.…”

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confidence: 99%

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Degradation of Ge subcells by thermal load during the growth of multijunction solar cells

Barrigón

Ochoa

García

et al. 2017

Progress in Photovoltaics

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Germanium solar cells are used as bottom subcells in many multijunction solar cell designs. The question remains whether the thermal load originated by the growth of the upper layers of the multijunction solar cell structure affects the Ge subcell performance. Here, we report and analyze the performance degradation of the Ge subcell due to such thermal load in lattice‐matched GaInP/Ga(In)As/Ge triple‐junction solar cells. Specifically, we have detected a quantum efficiency loss in the wavelength region corresponding to the emitter layer (which accounts for up to 20% loss in equivalent JSC) and up to 55 mV loss in VOC of the Ge subcell as compared with analogous devices grown as single‐junction Ge solar cells on the same type of substrates. We prove experimentally that there is no direct correlation between the loss in VOC and the doping level of the base. Our simulations show that both the JSC and VOC losses are consistent with a degradation of the minority carrier properties at the emitter, in particular at the initial nanometers of the emitter next to the emitter/window heterointerface. In addition, we also rule out the gradual emitter profile shape as the origin of the degradation observed. Our findings underscore the potential to obtain higher efficiencies in Ge‐based multijunction solar cells if strategies to mitigate the impact of the thermal load are taken into consideration.

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Section: Experimental and Modellingmentioning

confidence: 99%

mentioning

confidence: 99%

Degradation of Ge subcells by thermal load during the growth of multijunction solar cells

Barrigón

Ochoa

García

et al. 2017

Progress in Photovoltaics

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“…Particularly, P termination of the Ge surface should be obtained prior to nucleation for state-of-the-art GalnP on Ge heteroepitaxy in MOVPE [10,11]. Phosphine (PH 3 ) and tertiarybutylphosphine (TBP) are nowadays the two main P precursors used in MOVPE systems.…”

Section: Introductionmentioning

confidence: 99%

In situ study of Ge(100) surfaces with tertiarybutylphosphine supply in vapor phase epitaxy ambient

Barrigón¹,

Brückner²,

Supplie³

et al. 2013

Journal of Crystal Growth

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GalnP nucleation on Ge(100) often starts by annealing of the Ge(100) substrates under supply of phosphorus precursors. However, the influence on the Ge surface is not well understood. Here, we studied vicinal Ge(100) surfaces annealed under tertiarybutylphosphine (TBP) supply in MOVPE by in situ reflection anisotropy spectroscopy (RAS), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). While XPS reveals a P termination and the presence of carbon on the Ge surface, LEED patterns indicate a disordered surface probably due to by-products of the TBP pyrolysis. However, the TBP annealed Ge(100) surface exhibits a characteristic RA spectrum, which is related to the P termination. RAS allows us to in situ control phosphorus desorption dependent on temperature.

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“…The hydrogen coverage of the Ge surface during processing in H 2 ambient represents a dynamic balance of hydrogen adsorption and desorption events depending on the process parameters such as temperature and hydrogen pressure. Accordingly, Ge(100) is H‐free in H 2 process gas ambient at a H 2 pressure of 100 mbar for temperatures above 370 °C, and thus corresponding process conditions are typically used for III/V nucleation (420–750 °C, 50–100 mbar H 2 pressure) . In contrast to Si(100), there is no indication for etching processes induced by the H 2 interaction.…”

Section: Epitaxial Reference Surfacesmentioning

confidence: 99%

In Situ Characterization of Interfaces Relevant for Efficient Photoinduced Reactions

Supplie

May

Brückner

et al. 2017

Adv Materials Inter

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which he pioneered and established. In general, interfaces do not only determine electronic properties of the final device; their atomic order also highly affects growth kinetics and defect formation. Moreover, the design of solid-liquid and hybrid interfaces determines their chemical reactivity and stability. In situ monitoring of interface preparation, formation, and interfacial reactions thus promises efficient process control. Paired with a detailed understanding of interface formation mechanisms, however, the true power of in situ control is to allow for specific modification and tuning of interface formation for the device of choice. There are several excellent reviews on in situ approaches covering wide ranges of materials from basic science to applications as well as varieties of preparation and analysis techniques. [2][3][4][5][6][7][8][9][10][11] As indicated in Figure 1, this review will be focused on in situ control over interfaces of materials that are relevant for photoinduced reactions in high-efficiency solar energy conversion and sensing applications with in situ control of semiconductor/polymer/ biological interfaces. We will restrict the techniques to realistic and complex, non-ultrahigh-vacuum (UHV) ambient, where in situ control is most demandingbut also highly desired. The more complex the interfacial reactions are, the more important is the in situ characterization. Ex situ approaches can contribute to an indirect understanding of interface formation, but to understand and, finally, control the dynamic processes taking place, real-time measurements are appropriate. The challenge, we are facing, is twofold: On the one hand, increased interaction with the surrounding ambient causes higher complexity. Yet at the same time, it decreases the number of applicable techniques. On the other hand, those techniques are often elaborate and not necessarily easy to interpret. In a nutshell, we will discuss four main topics:(i) Surface preparation during growth of structures for highefficiency solar energy conversion: World-record conversion efficiencies in both photovoltaics [12,13] and solar water splitting [14] are achieved with multijunction solar cells based on epitaxial III/V compound semiconductor structures. We will discuss in situ controlled preparation Solar energy conversion and photoinduced bioactive sensors are representing topical scientific fields, where interfaces play a decisive role for efficient applications. The key to specifically tune these interfaces is a precise knowledge of interfacial structures and their formation on the microscopic, preferably atomic scale. Gaining thorough insight into interfacial reactions, however, is particularly challenging in relevant complex chemical environment. This review introduces a spectrum of material systems with corresponding interfaces significant for efficient applications in energy conversion and sensor technologies. It highlights appropriate analysis techniques capable of monitoring critical physicochemical reactions in situ during non-vacuu...

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Reflectance anisotropy spectroscopy assessment of the MOVPE nucleation of GaInP on germanium (1 0 0)

Cited by 23 publications

References 16 publications

Degradation of Ge subcells by thermal load during the growth of multijunction solar cells

Degradation of Ge subcells by thermal load during the growth of multijunction solar cells

In situ study of Ge(100) surfaces with tertiarybutylphosphine supply in vapor phase epitaxy ambient

In Situ Characterization of Interfaces Relevant for Efficient Photoinduced Reactions

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