A record $1 trillion of junk debt will mature by 2021, leaving high-risk companies to hunt for new cash at a time when markets are likely to be less welcoming, according to Moody’s Investors Service. Speculative-grade companies have $1.06 trillion of debt maturing between 2017 and 2021, with the bulk of it, $933 billion, coming due after 2019, Moody’s said Wednesday in a report.