If you're working for a U.S. technology firm, it's probably best not to steal trade secrets and set up a competing firm in China.

But that's what two former employees of Avago Technologies and Skyworks Solutions did, and one of them is now in custody on economic espionage charges.

Hao Zhang was arrested on Saturday as he tried to re-enter the U.S. from China. He's charged with conspiracy to commit economic espionage, conspiracy to commit theft of trade secrets, economic espionage, and theft of trade secrets. Wei Pang faces the same charges, but is not yet in custody.

According to the U.S. Justice Department, Zhang and Pang met at a California university when they were doctoral students studying engineering. After graduation, Pang went to work for Avago in Colorado and Zhang went to Massachusetts to work for Skyworks, where they both worked on networking technology that prevents interference on phones, tablets, and GPS devices, known as thin-film bulk acoustic resonator (FBAR).

In 2006 and 2007, however, Zhang and Pang started talking to Chinese universities to see if they could use information stolen from Avago and Skyworks to start their own rival firm in China. Tianjin University was interested, and helped the duo found ROFS Microsystem in 2009 to mass produce FBARs.

According to the indictment, "Pang, Zhang and other co-conspirators stole recipes, source code, specifications, presentations, design layouts and other documents marked as confidential and proprietary from the victim companies and shared the information with one another and with individuals working for Tianjin University."

Also included in the indictment is: Jinping Chen, a professor at Tianjin University and board of directors for ROFS Microsystems; Huisui Zhang, also a former student at the California university; Chong Zhou, a Tianjin University graduate student and a design engineer at ROFS Microsystem; and Zhao Gang, General Manager of ROFS Microsystems.

The economic espionage charges carry up to 15 years in prison, while conspiracy to commit theft of trade secrets could result in a decade behind bars.