RQM has built-in defect management support. It is available from the "Defects" flyover menu. You do not need RTC or CQ.
RQM builds on the same workitem/defect functionality that is present in RTC. In that vein, the available customization is the same as well. One word of warning: this customization is not formally supported yet and some of the RQM artifacts build on top of workitem and defect so you can indirectly affect them. The best course of action is additive changes or the creation of a new type while maintaining the existing workitem types in the process XML.
Hope that helps.
Regards,
John

Hi

Can RQM manage defects without RTC or ClearQuest? Where can I find the detailed information regarding defect process workflow (like old CQ state transition model)? Am I able to customize it, e.g. add more field, states? Or is it like CQ ALM?

Thanks
Jirong