What is the type of research when I use semi structured questionnaire, is it quantitative research or mixed research?

Semi structured questionnaire typically are used in qualitative research.  However, open ended questionnaire are also very commonly adopted in qualitative research.  Quantitative research typically used structured questionnaire in the form of survey etc.  Some mixed method research do use both structured questionnaire (in quantitative research section) & semi structured as well open ended questionnaire (in qualitative research section).

If it is mixed research, does it can be conducted without interview?

The qualitative research section of a mixed method research can use other data collection method beside interview i.e. depending on the research objective(s) & research requirements, some researchers do use some of the following methods:

The classic use of a semi-structured questionnaire is to gather data in an interview or focus group setting. Without the capacity to vary the order or phrasing of the questions, the questionnaire would not be semi-structured. Any written questionnaire would be in a fixed order for the participate to address questions in turn.

Whether the nature of the data collected is qualitative or quantitative depends on whether the questions asked are open- or closed-ended, so it is easy for a single questionnaire to collect both kinds of data in order to be a mixed method study.

After the data is collected, your method of analysis of the data may be qualitative (thematic interpretations) or quantitative (statistical analyses). Obviously, your choice of data collection and data analysis methodologies can take on several forms that might claim to be mixed methods.

What is the type of research when I use semi structured questionnaire, is it quantitative research or mixed research?

Semi structured questionnaire typically are used in qualitative research.  However, open ended questionnaire are also very commonly adopted in qualitative research.  Quantitative research typically used structured questionnaire in the form of survey etc.  Some mixed method research do use both structured questionnaire (in quantitative research section) & semi structured as well open ended questionnaire (in qualitative research section).

If it is mixed research, does it can be conducted without interview?

The qualitative research section of a mixed method research can use other data collection method beside interview i.e. depending on the research objective(s) & research requirements, some researchers do use some of the following methods:

 my dear, i agree with Han Ping Fung

I agree that semi-structured interviewing is almost always a qualitative method, but your question is so basic that I have to wonder whether you are prepared to do this kind of interviewing. Almost any introductory book on qualitative research will contain a section on semi-structured interviewing,.

Hi researcher,

When you say "semi-structured" then you mean that you ask your interviewees open-ended questions in an order that you wish to build an insight into a topic. It is solely used in qualitative research methods. 

Regards,

 Answers to semi-structured questions could also be quantified in some fashion and there are various techniques to do it. You might want to look up: "mixed method" and "quantifying qualitative data". 

McGoldrick, P. J., & Liu, C. (2017). Application of Mixed Methods by Consumer Marketing Practitioners: Lessons for the Academy? Abstract. In Creating Marketing Magic and Innovative Future Marketing Trends (pp. 1463-1464). Springer, Cham.

Rahman, K., & Areni, C. (2016). The benefits of quantifying qualitative brand data: A mixed-method approach for converting free brand associations to a brand equity index. International Journal of Market Research, 58(3), 421-450.

Best wishes!

I think there is nothing more to be added here besides emphasizing that there is a clear distinction between: (a) data collection method - which determines what type of data you have, and (b) the method of analysis - which determines what are you going to do with them. You need to take a look at both to understand whether what you do is actually quantitative, qualitative, or mixed method.

In case of semi-structured interviews it's rather qualitative method as it offers open-ended questions where the more interesting aspect is what people reveal to you on their own, rather than how they fit into the brackets you give them, based on the frame of your hypthesis. 

I also agree with David L. Morgan. You should probably check what the semi-structured interviews are to see whether it is actually how you want to conduct your study. Maybe Denzin and Lincoln's SAGE handbook of qualitative research would be a good place to start? (you should easily find it in your library)

All the best! :) 

whether it is quant or qual depends mostly on how you analyze your data; if you try to count responses and draw conclusions based on percentages who answer one way or another, it is a quant analysis; if you draw on the ideas and context of each interviewee's responses, if one person's insight weighs more in your study than ten people's knee jerk and canned response, then your analysis is qualitative.  I agree with Krzysztof on this issue.

I agree with the replies above. Just adding this: it also depends on how you start your research. Do you have research questions or hypothesis? The choices regarding techniques and tools to use to collect data surely depend on the method you use, nevertheless the method chosen should follow what you are searching for (in other words the questions you want to reply to with your study).