State-backed Chinese private equity firm Tsinghua Unigroup Ltd offered to buy U.S. memory chipmaker Micron Technology Inc for US$23 billion, The Wall Street Journal reported, citing people familiar with the matter. REUTERS: State-backed Chinese private equity firm Tsinghua Unigroup Ltd offered to buy U.S. memory chipmaker Micron Technology Inc for US$23 billion, The Wall Street Journal reported, citing people familiar with the matter.