You should seek the citation recommendation from the body that governs your research.
This is an evolving area, and university institutions are already collating guidance on how to properly cite LLM's.
E.g. For ChatGPT;
Author. (Year of the Version). Title of the Tool (Version if applicable) [Tool description if applicable]. Source/URL
Example: OpenAI. (2023). ChatGPT (Mar 14 version) [Large language model]. https://chat.openai.com/chat
Taking this suggested format for use with Azure OpenAI would result in something like this;
Azure AI Services (2023) OpenAI (gpt-35-turbo - version 0613) [Large language model]. https://learn.microsoft.com/en-us/azure/ai-services/openai